Upcoming

There are currently no upcoming events.

    Past

    All years2024202320222017

    All Events

    Special Guest Seminar

    Date:
    20
    Wednesday
    November
    2024
    Lecture / Seminar
    Time: 10:00-11:00
    Title: A formalism for Arithmetic Quantum Field Theory
    Location: Jacob Ziskind Building
    Lecturer: Nadav Gropper
    Organizer: Department of Mathematics
    Contact: hany.kochavi@weizmann.ac.il
    Abstract: Arithmetic Topology, first pioneered by Mazur in 1963, draws analogies between n ... Read more Arithmetic Topology, first pioneered by Mazur in 1963, draws analogies between number theory and low dimensional topology, primes and knots, and surface and p-adic fields. On one hand, quantum field theory can be expressed in terms of the geometry and topology of low-dimensional manifolds, on the level of states (via the Atiyah-Segal) and on the level of observables (via the Beilinson–Drinfeld). Thus, as first proposed by Minhyong Kim (in his Arithmetic Chern-Simons Theory), one can try and find arithmetic versions of quantum field theoretic ideas. In the talk, I will introduce a new general framework for (d 1)-dimensional arithmetic TQFT. I will explain the classification of such TQFTS for the (1 1)-dimensional case, in terms of Frobenius algebras with some extra structure, this enables us to study pro-p cobordisms and TQFTs for p-adic fields and surfaces at the same time.  If time permits, I will outline how we use the above to compute a Dijkgraaf-Witten like invariants for G, a finite p-group, to get formulas for counting covers of Surfaces/p-adic fields with Galois group G (these formulas are similar to the ones given by Mednykh for surfaces using TQFTs, and by Masakazu Yamagishi using a more algebraic approach). The talk is based on joint work with Oren Ben-Bassat. No prior knowledge of Topological Quantum Field Theory or Arithmetic Topology will be assumed.
    Close abstract

    Physics Colloquium

    Date:
    05
    Thursday
    September
    2024
    Colloquium
    Time: 11:15-12:30
    Title: New era in dark matter searches, the dawn of the nuclear clocks
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Gilad Perez
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: After a brief introduction related to ultralight (pseudo) scalar dark matter, we ... Read more After a brief introduction related to ultralight (pseudo) scalar dark matter, we shall describe the current status of searches for ultralight dark matter (UDM). We explain why modern clocks can be used to search for both scalar and axion dark matter fields. We review existing and new types of well-motivated models of UDM and argue that they all share one key ingredient - their dominant coupling is to the QCD/nuclear sector. This is very exciting as we are amidst a revolution in the field of dark matter searches as laser excitation of Th-229 with effective precision of 1:10^13 has been recently achieved, which as we show, is already probing uncharted territory of models. Furthermore, Th-229-based nuclear clock can potentially improve the sensitivity to physics of dark matter and beyond by factor of 10^10! It has several important implications to be discussed.
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    08
    Monday
    July
    2024
    Lecture / Seminar
    Time: 11:15-12:15
    Title: Quantum Algorithms in a Superposition of Spacetimes
    Location: Jacob Ziskind Building
    Lecturer: Omri Shmueli
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: Quantum computers are expected to revolutionize our ability to process informati ... Read more Quantum computers are expected to revolutionize our ability to process information. The advancement from classical to quantum computing is a product of our advancement from classical to quantum physics -- the more our understanding of the universe grows, so does our ability to use it for computation. A natural question that arises is, what will physics allow in the future? Can more advanced theories of physics increase our computational power, beyond quantum computing? An active field of research in physics studies theoretical phenomena outside the scope of explainable quantum mechanics, that form when attempting to combine Quantum Mechanics (QM) with General Relativity (GR) into a unified theory of Quantum Gravity (QG). QG is known to present the possibility of a quantum superposition of causal structure and event orderings. In the literature of quantum information theory, this translates to a superposition of unitary evolution orders. In this talk we will show a first example of a computational model based on models of QG, that provides an exponential speedup over standard quantum computation (under standard hardness assumptions). We define a model and complexity measure for a quantum computer that has the ability to generate a superposition of unitary evolution orders, and show that such computer is able to solve in polynomial time two well-studied problems in computer science: The Graph Isomorphism Problem and the Gap Closest Vector Problem, with gap O( n^{1.5} ).    The talk is based on https://arxiv.org/abs/2403.02937 .
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    June
    2024
    Lecture / Seminar
    Time: 11:15-12:15
    Title: Differentially Private Space-Efficient Algorithms for Frequency Moment Estimation in the Turnstile Model
    Location: Jacob Ziskind Building
    Lecturer: Rachel Cummings
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: hany.kochavi@weizmann.ac.il
    Abstract: The  turnstile continual release model of differential privacy captures scenari ... Read more The  turnstile continual release model of differential privacy captures scenarios where a privacy-preserving real-time analysis  is sought for a dataset evolving  through additions and deletions.  In typical applications of real-time data analysis, both the length of the stream T and the size of the universe |U| from which data come can be extremely large. This motivates the study of private algorithms in the turnstile setting using space sublinear in both T and |U|. In this paper, we give the first sublinear space differentially private algorithms for the fundamental problems of counting distinct elements and $ell_p$-frequency moment estimation in the turnstile streaming model. For counting distinct elements, our algorithm achieves O(T^{1/3}) space and additive error, and a (1 eta)-relative approximation for all eta in (0,1). Our result significantly improves upon the space requirements of the state-of-the-art for this problem in this model, which has a linear dependency in both T and |U|, while still achieving an additive error that is close to the known Omega(T^{1/4}) lower bound for arbitrary streams. This addresses an open question posed in prior work about designing low-memory mechanisms for this problem. For the more general problem of L_p-frequency moment estimation, our algorithm achieves an additive error and space of O(T^{1/3}), and a (1 eta)-relative approximation for all eta in (0,1). We also give a space lower bound for this problem, which shows that any algorithm that uses our techniques must use space Omega}(T^{1/3}). Joint work with Alessandro Epasto, Jieming Mao, Tamalika Mukherjee, Tingting Ou, and Peilin Zhong.
    Close abstract

    Physics colloquium

    Date:
    20
    Thursday
    June
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Stochastic resonance in polymer solution channel flow
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Victor Steinberg
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - Coffee, tea and refreshments
    Abstract: A cooperative resonance effect in a stochastic nonlinear dynamical system subjec ... Read more A cooperative resonance effect in a stochastic nonlinear dynamical system subjected to external weak periodic forcing, called stochastic resonance (SR), has been extensively studied for the past forty years. Here I discuss the experimentally unexpected observation of SR above an elastic non-modal instability of an inertia-less channel flow of polymer solution (much more complicated than stochastic dynamical flow) due to finite-size white noise perturbations. This flow is shown to be linearly stable similar to Newtonian parallel shear flow. First, I briefly describe viscoelastic flow with curved streamlines, where linear elastic normal mode instability at the critical Weissenberg number, Wic, has been observed and characterized, and the elastic instability mechanism has been explained and experimentally validated. Furthermore, at Wi>>Wic, “elastic turbulence” (ET), a chaotic flow arising via secondary instability, is experimentally discovered, characterized and theoretically explained, while elastic instability in straight channel flow is found from the direct transition from laminar to chaotic flow in the transition flow regime is found. At the secondary instability, ET is observed, and further on the next transition to the unexpected drag reduction flow regime takes place, accompanied by elastic waves previously discovered and characterized earlier. Moreover, we propose and experimentally validate a mechanism of amplification of the wall normal fluctuating vortices by the elastic waves. The elastic waves play the key role in the energy transfer from the main flow to the wall-normal fluctuating vortices. Finally, we report on recently discovered SRs only in a limited subrange of weak elastic waves just above Wic, their characterization, and their role in the transition to a chaotic flow.
    Close abstract

    Physics Colloquium

    Date:
    10
    Monday
    June
    2024
    Colloquium
    Time: 11:15-12:30
    Title: OBSERVATION OF FRACTIONAL QUANTUM ANOMALOUS HALL EFFECT
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Xiaodong Xu
    Organizer: Department of Condensed Matter Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Coffee and refreshments at 11:00
    Abstract: The interplay between spontaneous symmetry breaking and topology can result in e ... Read more The interplay between spontaneous symmetry breaking and topology can result in exotic quantum states of matter. A celebrated example is the quantum anomalous Hall (QAH) effect, which exhibits an integer quantum Hall effect at zero magnetic field due to topologically nontrivial bands and intrinsic magnetism. In the presence of strong electron-electron interactions, fractional-QAH (FQAH) effect at zero magnetic field can emerge, which is a lattice analog of fractional quantum Hall effect without Landau level formation. In this talk, I will present experimental observation of FQAH effect in twisted MoTe2 bilayer, using combined magneto-optical and -transport measurements. In addition, we find an anomalous Hall state near the filling factor -1/2, whose behavior resembles that of the composite Fermi liquid phase in the half-filled lowest Landau level of a two-dimensional electron gas at high magnetic field. Direct observation of the FQAH and associated effects paves the way for researching charge fractionalization and anyonic statistics at zero magnetic field. Reference 1. Observation of Fractionally Quantized Anomalous Hall Effect, Heonjoon Park et al., Nature, https://www.nature.com/articles/s41586-023-06536-0 (2023); 2. Signatures of Fractional Quantum Anomalous Hall States in Twisted MoTe2 Bilayer, Jiaqi Cai et al., Nature, https://www.nature.com/articles/s41586-023-06289-w (2023); 3. Programming Correlated Magnetic States via Gate Controlled Moiré Geometry, Eric Anderson et al., Science, https://www.science.org/doi/full/10.1126/science.adg4268 (2023).
    Close abstract

    AI (R)Evolution in (Quantum) Chemistry and Physics

    Date:
    10
    Monday
    June
    2024
    Colloquium
    Time: 11:00-12:15
    Title: Annual Pearlman Lecture
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Alexandre Tkatchenko
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: Learning from data has led to paradigm shifts in a multitude of disciplines, inc ... Read more Learning from data has led to paradigm shifts in a multitude of disciplines, including web, text and image search and generation, speech recognition, as well as bioinformatics. Can machine learning enable similar breakthroughs in understanding (quantum) molecules and materials? Aiming towards a unified machine learning (ML) model of molecular interactions in chemical space, I will discuss the potential and challenges for using ML techniques in chemistry and physics. ML methods can not only accurately estimate molecular properties of large datasets, but they can also lead to new insights into chemical similarity, aromaticity, reactivity, and molecular dynamics. For example, the combination of reliable molecular data with ML methods has enabled a fully quantitative simulation of protein dynamics in water (https://arxiv.org/abs/2205.08306). While the potential of machine learning for revealing insights into molecules and materials is high, I will conclude my talk by discussing the many remaining challenges.
    Close abstract
    AI (R)Evolution in (Quantum) Chemistry and Physics Colloquium website

    Physics Colloquium

    Date:
    06
    Thursday
    June
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Emergent Quantum Phenomena in Crystalline Multilayer Graphene
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Long Ju
    Organizer: Department of Condensed Matter Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Coffee and refreshments at 11:00
    Abstract: Condensed matter physics has witnessed emergent quantum phenomena driven by elec ... Read more Condensed matter physics has witnessed emergent quantum phenomena driven by electron correlation and topology. Such phenomena have been mostly observed in conventional crystalline materials where flat electronic bands are available. In recent years, moiré superlattices built upon two-dimensional (2D) materials emerged as a new platform to engineer and study electron correlation and topology. In this talk, I will introduce a family of synthetic quantum materials, based on crystalline multilayer graphene, as a new platform to engineer and study emergent phenomena driven by many-body interactions. This system hosts flat-bands in highly ordered conventional crystalline materials and dresses them with proximity effects enabled by rich structures in 2D van der Waals heterostructures. As a result, a rich spectrum of emergent phenomena including correlated insulators, spin/valley-polarized metals, integer and fractional quantum anomalous Hall effects, as well as superconductivities have been observed in our experiments. I will also discuss the implications of these observations for topological quantum computation. References: [1] Han, T., Lu, Z., Scuri, G. et al. Nat. Nanotechnol. 19, 181–187 (2024). [2] Han, T., Lu, Z., Scuri, G. et al. Nature 623, 41–47 (2023). [3] Han, T., Lu, Z., Yao, Y. et al. Science 384,647-651(2024). [4] Lu, Z., Han, T., Yao, Y. et al. Nature 626, 759–764 (2024). [5] Yang, J., Chen, G., Han, T. et al. Science, 375(6586), pp.1295-1299. (2022)
    Close abstract

    Midrasha on Groups Seminar

    Date:
    03
    Monday
    June
    2024
    Lecture / Seminar
    Time: 14:15-16:00
    Title: mod 2 cohomology, random simplicial complexes, property testing, and coboundry expansion
    Location: Jacob Ziskind Building
    Lecturer: Alex Lubotzky
    Organizer: Department of Mathematics
    Contact: hany.kochavi@weizmann.ac.il
    Details: The lecture will be frontal and also via zoom (pass: 400359)
    Abstract: We will start with an elementary introduction to mod 2 cohomology (only basic li ... Read more We will start with an elementary introduction to mod 2 cohomology (only basic linear algebra is needed). We will then see how it relates to the other topics in the title. If time permits, we will also say something about quantum error correcting codes.
    Close abstract

    Physics Colloquium

    Date:
    23
    Thursday
    May
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Quantum Dot Physics Using Atomic Defects in Ultrathin Tunnel Barriers
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Hadar Steinberg
    Organizer: Department of Condensed Matter Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: Quantum dots (QDs) are conducting regions which can localize few charge carriers ... Read more Quantum dots (QDs) are conducting regions which can localize few charge carriers, and where the energy spectrum is dominated by Coulomb repulsion. QDs can be as large as few hundreds of nanometers, or as small as a single molecule, their sizes depending on their physical realization – whether in two-dimensional materials, nanowires, molecular systems. In my talk I will describe our work on a new type of an atomically-sized QD, realized in defects residing in ultrathin two-dimensional insulators. These defect-dots are found in layered materials such as hexagonal Boron Nitride (hBN), which we study by their assembly into stacked devices. By using graphene electrodes, we are able to electronically couple to the QD, while allowing the QD energy to be externally tuned exploiting the penetration of electric field through graphene. A consequence of the structure of our devices is that the defect QDs are placed at atomic distance to the conductors on both sides. I will show how the presence of such energy-tunable, atomically sized QDs at nanometer proximity to other conducting systems opens new opportunities for sensitive measurements, including use of QDs as highly sensitive spectrometers [1], or as single electron transistors, unique in their sensitivity to local electric fields at the nanometer scale [2]. I will discuss our future prospects of using defect QDs as quantum sensors. References 1. Devidas, T.R., I. Keren, and H. Steinberg, Spectroscopy of NbSe2 Using Energy-Tunable Defect-Embedded Quantum Dots. Nano Letters, 2021. 21(16): p. 6931-6937. 2. Keren, I., et al., Quantum-dot assisted spectroscopy of degeneracy-lifted Landau levels in graphene. Nature Communications, 2020. 11(1): p. 3408.
    Close abstract

    Designing nanoparticles for biological environments: from quantum sensing to gene medicine

    Date:
    20
    Monday
    May
    2024
    Colloquium
    Time: 11:00-12:15
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Petr Cigler
    Organizer: Department of Chemical and Biological Physics
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: The use of nanoparticles in diagnostics, therapeutics and imaging has revolution ... Read more The use of nanoparticles in diagnostics, therapeutics and imaging has revolutionized these fields with new properties not available with small molecules. Nanoparticle interface provide possibilities for polyvalent and independent attachment of different molecules serving as recognition/targeting structures, optical probes, spin probes or catalysts. However, nanoparticles operating in biological environments require precise control of multiple factors related to surface chemistry and their composition. To avoid for example aggregation, off-target interactions, and protein corona formation, appropriate interface design is essential. This talk will present general nanoparticle design strategies and specific examples including nanodiamonds and lipid nanoparticles.
    Close abstract
    Designing nanoparticles for biological environments: from quantum sensing to gene medicine Colloquium website

    Physics Colloquium

    Date:
    16
    Thursday
    May
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Toward Autonomous “Artificial Cells” in 2D
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Roy Bar-Ziv
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: We study the assembly of programmable quasi-2D DNA compartments as “artificia ... Read more We study the assembly of programmable quasi-2D DNA compartments as “artificial cells” from the individual cellular level to multicellular communication. We will describe work on autonomous synthesis and assembly of cellular machines, collective modes of synchrony in a 2D lattice of ~1000 compartments, and a first look at the birth of proteins on a single DNA.
    Close abstract

    Physics colloquium

    Date:
    09
    Thursday
    May
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Synergistic progress in plasmas: from fusion to astrophysics
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Julien Fuchs
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: Over the last decade, several exciting directions have been initiated by laser-d ... Read more Over the last decade, several exciting directions have been initiated by laser-driven plasmas, e.g., compact particle accelerators, inertial fusion and laboratory astrophysics. The first has known rapid progress, in terms of current, energy, stability; fusion has gone through a historic step, with the news of ignition being achieved at NIF in 2022; and laboratory astrophysics has known also spectacular developments, demonstrating the possibility to perform fully scalable experiments relevant to various objects such as forming stars and supernovae. A particularly interesting aspect is that all these fields are strongly synergistic, i.e., that advances in one can push the others as well. I will present examples of such synergies, through recent results we have obtained in all these domains, and in particular how ultra-bright neutron beams can be developed using latest generation multi-PW lasers [1,2]. These could open interesting perspectives in terms of cargo inspection, but also for fusion plasma measurements. I will also show how fusion can benefit from external magnetization [3]. Finally, I will discuss advances in laboratory astrophysics, particularly the first-stage acceleration of ions leading to cosmic rays [4,5], understanding the universal nature of collimated outflows in the Universe [6], and probing the intricacy of 3D magnetic reconnection [7] [1] High-flux neutron generation by laser-accelerated ions from single-and double-layer targets, V Horný et al., Scientific Reports 12 (1), 19767, 2022 [2] Numerical investigation of spallation neutrons generated from petawatt-scale laser-driven proton beams, B Martinez et al., Matter and Radiation at Extremes 7 (2), 024401, 2022 [3] Dynamics of nanosecond laser pulse propagation and of associated instabilities in a magnetized underdense plasma, W. Yao et al., https://doi.org/10.48550/arXiv.2211.06036 [4] Laboratory evidence for proton energization by collisionless shock surfing, W Yao et al., Nature Physics 17 (10), 1177-1182, 2021 [5] Enhancement of the Nonresonant Streaming Instability by Particle Collisions, A Marret et al., Physical Review Letters 128 (11), 115101, 2022 [6] Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field, G Revet et al., Nature communications 12 (1), 762, 2021 [7] Laboratory evidence of magnetic reconnection hampered in obliquely interacting flux tubes, S Bolaños et al., Nature Communications 13 (1), 6426, 2022
    Close abstract

    Data Drought in the Humid Tropics: How to Overcome the Cloud Barrier in Greenhouse Gas Remote Sensing

    Date:
    07
    Tuesday
    May
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Yinon Bar-On
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: Quantifying land-atmosphere fluxes of carbon-dioxide (CO2) and methane (CH4) is ... Read more Quantifying land-atmosphere fluxes of carbon-dioxide (CO2) and methane (CH4) is essential for evaluating carbonclimate feedbacks. Greenhouse gas satellite missions aim to provide global observational coverage of greenhouse gas concentrations and thus improve inversions of landatmosphere exchange fluxes. However, in key regions such as the humid tropics current missions obtain very few valid measurements. Leveraging recent advances in the global analysis of high-resolution optical imagery on cloudcomputing platforms and deep learning algorithms for cloud segmentation, we quantitatively diagnose the sources for low data yields in the tropics. We find that the main cause for low data yields are frequent shallow cumulus clouds. We find that increasing the spatial resolution of observations to 200 m would increase yields by 2–3 orders of magnitude and allow regular measurements in the wet season. Thus, the key to effective tropical greenhouse gas observations likely lies in regularly acquiring high-spatial resolution data.
    Close abstract

    Toward Autonomous “Artificial Cells” in 2D

    Date:
    11
    Thursday
    April
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Physics colloquium
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Roy Bar-Ziv
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: We study the assembly of programmable quasi-2D DNA compartments as “artificial ... Read more We study the assembly of programmable quasi-2D DNA compartments as “artificial cells”, from the individual cellular level to multicellular communication. We will describe work on autonomous synthesis and assembly of cellular machines, collective modes of synchrony in a 2D lattice of ~1000 compartments, and a first look at the birth of proteins on a single DNA.
    Close abstract

    Chemical Exfoliation of Quantum Materials

    Date:
    10
    Wednesday
    April
    2024
    Colloquium
    Time: 11:00-12:15
    Title: Special Colloquium
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Leslie M. Schoop
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: A large portion of research in 2D materials is limited to mechanical exfoliation ... Read more A large portion of research in 2D materials is limited to mechanical exfoliation of van der Waals (vdW) materials. Chemical exfoliation is a relatively under-utilized route for preparing ultra-thin quantum materials, but it accesses 2D materials that cannot be obtained by mechanical “Scotch -taping.'” It is also a way to mass produce 2D materials, as mechanical taping only accesses small amounts, insufficient for industrial applications. However, chemical exfoliation comes with the drawback that it commonly introduces many defects into the 2D sheets. In this talk I will show the challenges of using chemical exfoliation for 2D quantum materials synthesis, to then introduce two systems in which the approach was successful. I will show that we can use chemical exfoliation to synthesize large qualities of stable and magnetic monolayers of VOCl. Films of these high-quality sheets are shown to possess similar magnetic properties as the bulk crystals. I will also discuss the synthesis of a stable, aqueous ink of superconducting 1T'-WS2 monolayers. Films printed with the ink are superconducting below 7.3 K and show typical behavior of 2D superconductivity. This ink and its dried, printed version, is stable in ambient conditions. It is ideally suited for applications in flexible and printed electronics. Thus, we were able to establish that chemical exfoliation is of use for quantum materials synthesis.
    Close abstract
    Chemical Exfoliation of Quantum Materials Colloquium website

    Physics Colloquium

    Date:
    04
    Thursday
    April
    2024
    Colloquium
    Time: 11:15-12:30
    Title: The Rolling Stones, All Down the Line
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Tsvi Tlusti
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments will be served at 11:00
    Abstract: Draw an arbitrary open curve on the plane and copy it multiple times to form a t ... Read more Draw an arbitrary open curve on the plane and copy it multiple times to form a translationally invariant infinite trajectory. Then, incline the plane slightly and ask yourself: can one chisel a stone that will roll exactly down this infinite trajectory? We will examine this question in practice and theory. Intriguing links to optics and quantum systems will be discussed. Bringing a tennis ball or a baseball is always recommended. Eckmann et al. Tumbling downhill along a given curve. Am Math Soc Notices - in press. Sobolev et al. Solid-body trajectoids shaped to roll along desired pathways. Nature 2023.
    Close abstract

    Large scale circulation adjustments to aerosol-cloud interactions and its radiative effect

    Date:
    31
    Sunday
    March
    2024
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Guy Dagan
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: The impact of anthropogenic aerosols on clouds is a leading source of uncertaint ... Read more The impact of anthropogenic aerosols on clouds is a leading source of uncertainty in estimating the effect of human activity on the climate system. The challenge lies in the scale difference between clouds (~1-10 km) and general circulation and climate (~1000 km). To address this, we utilize three different novel sets of simulations that allow to resolve convection while also including a epresentation of large-scale processes. Our findings demonstrate that aerosol-cloud interaction intensifies tropical overturning circulation. Employing a weak temperature gradient approximation, we attribute variations in circulation to clear-sky humidity changes driven by warm rain suppression by aerosols. In two sets of simulations accounting for sub-tropical-tropical coupling, we show that aerosol-driven sub-tropical rain suppression leads to increased advection of cold and moist air from the sub-tropics to the tropics, thus enhancing tropical cloudiness. The increased tropical cloudiness has a strong cooling effect by reflecting more of the incoming solar radiation. The classical “aerosol-cloud lifetime effect” is shown here to have a strong remote effect (sub-tropical aerosols increase cloudiness in the tropics), thus widening the concept of cloud adjustments to aerosol perturbation with important implications for marine cloud brightening.
    Close abstract

    Physics Colloquium

    Date:
    21
    Thursday
    March
    2024
    Colloquium
    Time: 11:15-12:30
    Title: Fractional statistics of anyons in mesoscopic colliders
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Gwendal Fève
    Organizer: Department of Condensed Matter Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments will be served at 11:00
    Abstract: In three-dimensional space, elementary particles are divided between fermions an ... Read more In three-dimensional space, elementary particles are divided between fermions and bosons according to the properties of symmetry of the wave function describing the state of the system when two particles are exchanged. When exchanging two fermions, the wave function acquires a phase, φ=π. On the other hand, in the case of bosons, this phase is zero, φ=0. This difference leads to deeply distinct collective behaviors between fermions, which tend to exclude themselves, and bosons which tend to bunch together. The situation is different in two-dimensional systems which can host exotic quasiparticles, called anyons, which obey intermediate quantum statistics characterized by a phase φ varying between 0 and π [1,2]. For example in the fractional quantum Hall regime, obtained by applying a strong magnetic field perpendicular to a two-dimensional electron gas, elementary excitations carry a fractional charge [3,4] and have been predicted to obey fractional statistics [1,2] with an exchange phase φ=π/m (where m is an odd integer). Using metallic gates deposited on top of the electron gas, beam-splitters of anyon beams can be implemented. I will present how the fractional statistics of anyons can be revealed in collider geometries, where anyon sources are placed at the input of a beam-splitter [5,6]. The partitioning of anyon beams is characterized by the formation of packets of anyons at the splitter output. This results in the observation of strong negative correlations of the electrical current, which value is governed by the anyon fractional exchange phase φ [5,7]. [1] B. I. Halperin, Phys. Rev. Lett. 52, 1583–1586 (1984). [2] D. Arovas, J. R. Schrieffer, F. Wilczek, Phys. Rev. Lett. 53, 722–723 (1984). [3] R. de Picciotto et al., Nature 389, 162–164 (1997). [4] L. Saminadayar, D. C. Glattli, Y. Jin, B. Etienne, Phys. Rev. Lett. 79, 2526–2529 (1997) [5] B. Rosenow, I. P. Levkivskyi, B. I. Halperin, Phys. Rev. Lett. 116, 156802 (2016). [6] H. Bartolomei et al. Science 368, 173-177 (2020). [7] Lee, JY.M., Sim, HS, Nature Communications 13, 6660 (2022).
    Close abstract

    STATISTICAL MECHANICS DAY XV

    Date:
    19
    Tuesday
    March
    2024
    Conference
    Time: 08:00
    Location: Nella and Leon Benoziyo Physics Library
    Organizer: Department of Physics of Complex Systems
    Contact: oren.raz@weizmann.ac.il
    STATISTICAL MECHANICS DAY XV Conference website

    50 Shades of Molecular Modeling in Biomolecular Sciences

    Date:
    05
    Tuesday
    March
    2024
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Dr. Sofya Lushchekina
    Organizer: Department of Biomolecular Sciences
    Contact: levana.ayvazo@weizmann.ac.il
    Details: Scientific Consultant Israel Silman (invited by Moshe Goldsmith)
    Abstract: The presentation will cover a spectrum of current applications of atomistic mole ... Read more The presentation will cover a spectrum of current applications of atomistic molecular modeling methods in biomolecular problems. Examples of applications of molecular docking, molecular dynamics, combined quantum mechanics/molecular mechanics and dynamics methods, enhanced sampling, and coarse-graining methods, recent machine learning protein structure prediction methods for studying protein structure and dynamics, protein-ligand and protein-protein interactions, and mechanisms of enzymatic reactions will be considered. The advantages and limitations of different computational methods will be discussed.
    Close abstract

    Chemical and Biological Physics Guest seminar

    Date:
    07
    Wednesday
    February
    2024
    Lecture / Seminar
    Time: 15:00-16:00
    Title: The Stark effect in quantum dots: from spectral diffusion to coherent control
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Ron Tenne
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: While colloidal quantum dots (CQDs) are already an important building block in e ... Read more While colloidal quantum dots (CQDs) are already an important building block in electro-optical devices, in the realm of quantum science and technology, they are often considered inferior with respect to emitters such as solid-state defects and epitaxial quantum dots. Despite their single-photon emission [1], demonstrations of quantum coherence and control are largely still lacking. The main obstacle towards these is spectral diffusion – stochastic fluctuations in the energy of photons emitted from an individual CQD even at cryogenic temperatures. In this talk, I will present our recent work providing, for the first time, direct and definitive proof that these fluctuations arise from stochastic electric fields in the particle’s nano environment [2]. However, the high sensitivity of CQDs to electric fields, through the quantum-confined Stark effect, can also be perceived as a feature, rather than a bug. I will present future concepts for coherent control of a single photon’s temporal wavefunction through an electric bias. Relying on tools from the terahertz and femtosecond-laser toolboxes [3,4], spectroscopy and control at fast-to-ultrafast (millisecond-to-femtosecond) timescales, will play a detrimental role in fulfilling the unique potential that CQDs hold in the field of quantum optics,. [1] R. Tenne, U. Rossman, B. Rephael, Y. Israel, A. Krupinski-Ptaszek, R. Lapkiewicz, Y. Silberberg, and D. Oron, Super-Resolution Enhancement by Quantum Image Scanning Microscopy, Nature Photonics 13, 116 (2019). [2] F. Conradt, V. Bezold, V. Wiechert, S. Huber, S. Mecking, A. Leitenstorfer, and R. Tenne, Electric-Field Fluctuations as the Cause of Spectral Instabilities in Colloidal Quantum Dots, Nano Lett. 23, 9753 (2023). [3] P. Henzler et al., Femtosecond Transfer and Manipulation of Persistent Hot-Trion Coherence in a Single CdSe/ZnSe Quantum Dot, Physical Review Letters 126, 067402 (2021). [4] P. Fischer, G. Fitzky, D. Bossini, A. Leitenstorfer, and R. Tenne, Quantitative Analysis of Free-Electron Dynamics in InSb by Terahertz Shockwave Spectroscopy, Physical Review B 106, 205201 (2022).
    Close abstract

    The Clore Center for Biological Physics

    Date:
    21
    Sunday
    January
    2024
    Lecture / Seminar
    Time: 13:15-14:15
    Title: How informative are structures of dna-bound proteins for revealing binding mechanisms inside cells? the case of the Origin of Replication Complex (ORC)
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Prof. Naama Barkai
    Organizer: Department of Physics of Complex Systems
    Contact: malka.avraham@weizmann.ac.il
    Details: Lunch at 12:45
    Abstract: The Origin Recognition Complex (ORC) seeds the replication-fork by binding DNA r ... Read more The Origin Recognition Complex (ORC) seeds the replication-fork by binding DNA replication origins, which in budding yeast contain a 17bp DNA motif. High resolution structure of the ORC-DNA complex revealed two base-interacting elements: a disordered basic patch (Orc1-BP4) and an insertion helix (Orc4-IH). To define ORC elements guiding its DNA binding in-vivo, we mapped genomic locations of 38 designed ORC mutants. We revealed that different ORC elements guide binding at different motifs sites, and these correspond only partially to the structure- described interactions. In particular, we show that disordered basic patches are key for ORC-motif binding in-vivo, including one lacking from the structure. Finally i will discuss how those disordered elements, which insert into the minor-groove can still guide specific ORC-DNA recognition.
    Close abstract

    quantum error-correction meets high dimensional expansion, complexity hops on the boat

    Date:
    07
    Sunday
    January
    2024
    -
    10
    Wednesday
    January
    2024
    Conference
    Time: 08:00
    Location: The David Lopatie Conference Centre
    Organizer: The Center for Quantum Science and Technology,Department of Computer Science and Applied Mathematics
    Contact: irit.dinur@weizmann.ac.il
    quantum error-correction meets high dimensional expansion, complexity hops on the boat Conference website

    Chemical and Biological Physics Guest seminar

    Date:
    03
    Wednesday
    January
    2024
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Atomic arrays as programmable quantum processors and sensors
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Ran Finkelstein
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: Large arrays of trapped neutral atoms have emerged over the past few years as a ... Read more Large arrays of trapped neutral atoms have emerged over the past few years as a promising platform for quantum information processing, combining inherent scalability with high-fidelity control and site-resolved readout. In this talk, I will discuss ongoing work with arrays of Alkaline-earth atoms. These divalent atoms offer unique properties stemming largely from their long-lived metastable states, which form the basis of the optical atomic clock. I will describe the design of a universal quantum processor based on clock qubits and its application in quantum metrology, and I will address the challenge of generating and benchmarking highly entangled states in an analog quantum simulator. First, we realize scalable local control of individual clock qubits, which we utilize to extend the Ramsey interrogation time beyond the coherence time of a single atom [1]. To realize a universal quantum processor, we demonstrate record high-fidelity two-qubit entangling gates mediated by Rydberg interactions, which we combine with dynamical reconfiguration to entangle clock probes in GHZ states and perform Ancilla-based detection [2]. We then use the narrow clock transition to measure and remove thermal excitations of atoms in tweezers (a technique known as erasure conversion) and generate hyperentangled states of motion and spin [3]. In the second part of the talk, I will describe a different approach for generating large scale entangled states in an analog quantum simulator configuration [4], including error mitigation [5] and benchmarking of a 60-atom simulator [6]. Together, these show the great promise and the large variety of experiments accessed with this emerging platform. [1] A. Shaw*, R. Finkelstein*, R. Tsai, P. Scholl, T. Yoon, J. Choi, M. Endres, Multi-ensemble metrology by programming local rotations with atom movements, arxiv:2303.16885, Nature Physics in press (2023). [2] R. Finkelstein, R. Tsai, A. Shaw, X. Sun, M. Endres, A universal quantum processor for entanglement enhanced optical tweezer clocks, in preparation. [3] P. Scholl*, A. Shaw*, R. Finkelstein*, R. Tsai, J. Choi, M. Endres, Erasure cooling, control, and hyper-entanglement of motion in optical tweezers, arXiv:2311.15580 (2023). [4] J. Choi, A. Shaw, I. Madjarov, X. Xie, R. Finkelstein, J. Covey, J. Cotler, D. Mark, H.Y. Huang, A. Kale, H. Pichler, F. Brandão, S. Choi, and M. Endres, Preparing random states and benchmarking with many-body quantum chaos, Nature 617 (2023) [5] P. Scholl, A. Shaw, R. Tsai, R. Finkelstein, J. Choi, M. Endres, Erasure conversion in a high-fidelity Rydberg quantum simulator, Nature 622 (2023). [6] A. Shaw, Z. Chen, J. Choi, D.K. Mark, P. Scholl, R. Finkelstein, A. Elben, S. Choi, M. Endres, Benchmarking highly entangled states on a 60-atom analog quantum simulator, arXiv:2308.07914 (2023).
    Close abstract

    Geometric Functional Analysis and Probability Seminar

    Date:
    21
    Thursday
    December
    2023
    Lecture / Seminar
    Time: 13:30-14:30
    Title: Gaps of Fourier Quasicrystals and Lee-Yang Polynomials
    Location: Jacob Ziskind Building
    Lecturer: Lior Alon
    Organizer: Department of Mathematics
    Contact: hany.kochavi@weizmann.ac.il
    Abstract: The concept of "quasi-periodic" sets, functions, and measures is prevalent in ... Read more The concept of "quasi-periodic" sets, functions, and measures is prevalent in diverse mathematical fields such as Mathematical Physics, Fourier Analysis, and Number Theory. The Poisson summation formula provides a “Fourier characterization” for discrete periodic sets, saying that the Fourier transform of the counting measure of a discrete periodic set is also a counting measure of a discrete periodic set. Fourier Quasicrystals (FQ) generalize this notion of periodicity: a counting measure of a discrete set is called a Fourier quasicrystal (FQ) if its Fourier transform is also a discrete atomic measure, together with some growth condition.      Recently Kurasov and Sarnak provided a method for construction of one-dimensional counting measures which are FQ (motivated by quantum graphs) using the torus zero sets of multivariate Lee-Yang polynomials. In this talk, I will show that the Kurasov-Sarnak construction generates all FQ counting measures in 1D.   A discrete set on the real line is fully described by the gaps between consecutive points. A discrete periodic set has finitely many gaps. We show that a non-periodic FQ has uncountably many gaps, with a well-defined gap distribution. This distribution is given explicitly in terms of an ergodic dynamical system induced from irrational flow on the  torus.   The talk is aimed at a broad audience, no prior knowledge in the field is assumed.   Based on joint works with Alex Cohen and Cynthia Vinzant.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    30
    Thursday
    November
    2023
    Colloquium
    Time: 11:15-12:30
    Title: The Large Array Survey Telescope
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Eran Ofek
    Organizer: Department of Particle Physics and Astrophysics
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments will be served at 11:00
    Abstract: We are building a new ground-based observatory in Neot Smadar, located in the so ... Read more We are building a new ground-based observatory in Neot Smadar, located in the south of the Negev desert. One of the telescopes hosted at this site is the Large Array Survey Telescope (LAST). LAST is a cost-effective survey telescope capable of quickly scanning the sky and studying the dynamic sky, from solar system objects to explosions at cosmological distances. I will describe the Neot Smadar site, the LAST system, and some of the science cases for which LAST was built.
    Close abstract

    TBA

    Date:
    12
    Thursday
    October
    2023
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Julien Fuchs
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments will be served at 11:00
    Abstract: TBA ... Read more TBA
    Close abstract

    How storm develops as the wind blows

    Date:
    05
    Thursday
    October
    2023
    Colloquium
    Time: 11:00-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Gregory Falkovich
    Organizer: Department of Physics of Complex Systems
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments will be served at 11:00
    Abstract: I will describe an attempt to describe turbulence using the methods of quantum f ... Read more I will describe an attempt to describe turbulence using the methods of quantum field theory. We consider waves that interact via four-wave scattering (such as sea waves, plasma waves, spin waves, and many others). By summing the series of the most UV-divergent terms in the perturbation theory, we show that the true dimensionless coupling is different from the naive estimate, and find that the effective interaction either decays or grows explosively with the cascade extent, depending on the sign of the new coupling. The explosive growth possibly signals the appearance of a multi-wave bound state (solitons, shocks, cusps) similar to confinement in quantum chromodynamics.
    Close abstract

    Chemical and Biological and Ben May Seminar

    Date:
    14
    Thursday
    September
    2023
    Lecture / Seminar
    Time: 11:00
    Title: MRSF-TDDFT: Multi-Reference Advantages with The Practicality of Linear Response Theory
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Cheol Ho Choi
    Organizer: Ben May Center for Chemical Theory and Computation
    Contact: eli.pollak@weizmann.ac.il
    Abstract: A new quantum theory, MRSF-TDDFT (Mixed-Reference Spin-Flip Time-Dependent Densi ... Read more A new quantum theory, MRSF-TDDFT (Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory) has been developed*, which introduces the multi-reference advantages within the linear response formalism. The density functional theory (DFT) and linear response (LR) time dependent (TD)-DFT are of utmost importance for routine computations. However, the single reference formulation of DFT is suffering from the description of open-shell singlet systems such as diradicals and bond-breaking. LR-TDDFT, on the other hand, finds difficulties in the modeling of conical intersections, doubly excited states, and core-level excitations. Many of these limitations can be overcome by MRSF-TDDFT, providing an alternative yet accurate route for such challenging situations. Now the theory is combined with NAMD, QM/MM, Spin-Orbit Couplings, and Extended Koopman Theorem. Here, we highlight its performances by presenting our recent results by MRSF-TDDFT especially focusing on nonadiabatic molecular dynamics.
    Close abstract

    Physics Colloquium

    Date:
    29
    Thursday
    June
    2023
    Colloquium
    Time: 11:15-12:30
    Title: Quantum Materials: A View from the Lattice
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof Joe Checkelsky
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 Coffee, tea and more...
    Abstract: Connecting theoretical models for exotic quantum states to real materials is a k ... Read more Connecting theoretical models for exotic quantum states to real materials is a key goal in quantum materials science. The structure of the crystalline lattice plays a foundational role in this pursuit in the subfield of quantum material synthesis. We here revisit this long-standing perspective in the context low dimensional emergent electronic phases of matter. In particular, we discuss recent progress in realizing new lattice and superlattice motifs designed to address model topological and correlated electronic phenomena. We comment on the perspective for realizing further 2D model systems in complex material structures and connections to further paradigms for programmable quantum matter.
    Close abstract

    Integrating Crop Models and Satellite Data for Crop Yield Forecasts; and what NASA is looking for in Ukraine?

    Date:
    27
    Tuesday
    June
    2023
    Lecture / Seminar
    Time: 11:30-12:30
    Location: Zoom: https://weizmann.zoom.us/j/91461145626?pwd=QWkzc0xzNndpL3daTDIxdHJPQUlaZz09
    Lecturer: Dr. Yuval Sadeh
    Organizer: Department of Plant and Environmental Sciences
    Contact: david.zeevi@weizmann.ac.il

    Physics colloquium

    Date:
    26
    Monday
    June
    2023
    Colloquium
    Time: 11:15-12:30
    Title: Quantum control of dynamical states with switching times exceeding ten seconds
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof Zaki Leghtas
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more..
    Abstract: Macroscopic switching times between two stable states are widespread in science ... Read more Macroscopic switching times between two stable states are widespread in science and engineering. Common examples are the reversal of earth's magnetic field, or bit-flips in computer memories. Remarkably, long switching times persist even in systems at wildly reduced scales, such as oscillators containing only a handful of photons. Despite far reaching implications in quantum information science, preparing and measuring quantum superpositions of long-lived dynamical states has remained out of reach. Previous attempts achieved quantum control by introducing ancillary systems that in turn propagated errors limiting the switching times in the millisecond range. In this work, we implement a bistable dynamical system in a nonlinearly dissipative superconducting oscillator with an embedded parametric tool for quantum control and tomography. Through direct Wigner tomography, we observe quantum superpositions of dynamical states with switching times up to twenty seconds. Using quantum Zeno dynamics, we control the phase of these superpositions, and observe coherent oscillations decaying on the scale of hundreds of nanoseconds. This experiment demonstrates the encoding of quantum information in macroscopically stable dynamical states, promising shortcuts in the emergence of quantum technologies. Refs : Leghtas et al. Science 347, 853 (2015). Lescanne et al. Nature Physics 16, 509 (2020). Berdou et al. PRX Quantum preprint arXiv:2204.09128.
    Close abstract

    Physics Colloquium

    Date:
    22
    Thursday
    June
    2023
    Colloquium
    Time: 11:15-12:30
    Title: Seeking the Closest Habitable-Zone Planets
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Suvrath Mahadevan
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Coffee, Tea and more...
    Abstract: The discovery of planets capable of hosting biosignatures, and the characterizat ... Read more The discovery of planets capable of hosting biosignatures, and the characterization of the atmospheres of these planets, is a key and achievable goal in our lifetime. These goals require some of the most demanding precision spectroscopic and photometric measurements. I will discuss the instrumental challenges of detecting such planets with the Doppler radial velocity technique, and the evolution of the design of these instruments as they seek ever-tighter control of environmental parameters, and increased measurement precision. A suite of new technologies like frequency stabilized laser combs, low drift etalons, and deeper understanding of the detectors is enabling a new level of precision in radial velocity measurements - as well as illustrating new challenges. I will then discuss how the stars themselves are the remaining challenge, as magnetically driven processes create ‘stellar activity’ noise that can masquerade as planets and obfuscate their detection, and I highlight a few paths to mitigate this, along with some of the latest scientific results from the HPF and NEID instruments. I will discuss one iteration of a possible future, weaving its way from now through JWST individual and mini-population studies of planet atmospheres, large population studies with missions like ARIEL, the near-future of RV surveys, detection and characterization prospects with large ground-based, and the challenges and opportunities with future imaging and spectroscopic missions like LUVOIR and LIFE. The goal of discovering and characterizing terrestrial mass planets capable of hosting liquid water on their surfaces may now be within reach! But true understanding of the origin and meaning of the biosignatures we detect will likely require transdisciplinary research across multiple fields.
    Close abstract

    Physics Colloquium

    Date:
    15
    Thursday
    June
    2023
    Colloquium
    Time: 11:15-12:30
    Title: Search for quantum applications and taking POCs to production
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Helmut Katzgraber
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 Coffee, tea and more...
    Abstract: The Amazon Quantum Solutions Lab works closely with enterprise customers to iden ... Read more The Amazon Quantum Solutions Lab works closely with enterprise customers to identify use cases where quantum technologies might have impact in the fault-tolerant future, but also to develop creative ways to solve complex business challenges at scale today. In this presentation, I will showcase selected customer use cases and discuss where and when quantum machines can have an impact.
    Close abstract

    Chemical and Biological Physics Guest Seminar

    Date:
    15
    Thursday
    June
    2023
    Lecture / Seminar
    Time: 11:00
    Title: Ratchet based ion pumps
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Gideon Segev
    Organizer: Department of Chemical and Biological Physics
    Contact: omer.yaffe@weizmann.ac.il
    Abstract: Even though highly selective ion pumps can be found in every living cell membran ... Read more Even though highly selective ion pumps can be found in every living cell membrane, artificial, membrane-based ion selective separation is a longstanding unmet challenge in science and engineering. The development of a membrane-based ion separation technology can drive a dramatic progress in a wide range of applications such as: water treatment, bio-medical devices, extraction of precious metals from sea water, chemical sensors, solar fuels and more. In this seminar I will discuss our theoretical and experimental demonstration of ion pumps based on an electronic flashing ratchet mechanism. Electronic flashing ratchets are devices that utilize modulation in a spatially varying electric field to drive steady state current. Like peristaltic pumps, where the pump mechanism is not in direct contact with the pumped fluid, electronic ratchets induce net current with no direct charge transport between the power source and the pumped charge carriers. Thus, electronic ratchets can be used to pump ions in steady state with no electrochemical reactions between the power source and the pumped ions resulting in an “all electric” ion pump. Ratchet-based ion pumps (RBIPs) were fabricated by coating the two surfaces of nano-porous alumina wafers with gold forming nano-porous capacitor-like devices. The electric field within the nano-pores is modulated by oscillating the capacitors voltage. Thus, when immersed in solution, ions within the pores experience a modulating electric field resulting in ratchet-based ion pumping. The RBIPs performance was studied for various input signals, geometries, and solutions. RBIPs were shown to drive ionic current densities of several μA/cm2 even when opposed by an electrostatic force. A significant ratchet action was observed with input signal amplitudes as low as 0.1V thus demonstrating that RBIPs can drive an ionic current with no associated redox reactions. Simulations show that frequency dependent flux inversions in ratchet systems may pave the way towards ion selective RBIPs.
    Close abstract

    Joint Chemical and Biological Physics and Molecular Chemistry and Materials Science Guest Seminar

    Date:
    13
    Tuesday
    June
    2023
    Lecture / Seminar
    Time: 10:00-11:00
    Title: Tunneling and Zero-Point Energy Effects in Multidimensional Hydrogen Transfer Reactions
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Yair Litman
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: ydrogen transfer reactions play a prominent role in nature and many technologica ... Read more ydrogen transfer reactions play a prominent role in nature and many technological applications. Despite appearing to be simple reactions, they constitute complex processes where nuclear quantum effects (NQE) such as zero-point energy and nuclear tunneling play a decisive role even at ambient temperature. In this talk, I will show how state-of-the-art methodologies based on the path integral formulation of quantum mechanics in combination with the density functional approximation provide the unique possibility to theoretically address these effects in complex environments. The first part of the talk will focus on the porphycene molecule in the gas phase and adsorbed on metallic surfaces. The porphycene molecule constitutes a paradigmatic example of a molecular switch and has recently received great attention due to its intriguing hydrogen dynamics. I will demonstrate how a correct treatment of NQE, as well as the inclusion of multidimensional anharmonic couplings, are essential to obtain qualitatively correct results regarding the non-trivial temperature dependence of the hydrogen transfer rates and vibrational spectra [1-3]. Finally, I shall also mention some of our recent results for hydrogen diffusion on metals for which non-adiabatic effects, in addition to NQE, play a significant role and can lead to “quantum localization” [4-6]. [1] Y. Litman, J. O. Richardson, T. Kumagai, and M. Rossi, J. Am. Chem. Soc. 141, 2526 (2019) [2] Y. Litman, J. Behler, and M. Rossi, Faraday Discuss. 221, 526 (2020) [3] Y. Litman and M. Rossi, Phys. Rev. Lett. 125, 216001 (2020) [4] Y. Litman, E. S. Pos. C. L. Box, R. Martinazzo, R. J. Maurer, and M. Rossi, J. Chem. Phys. 156, 194106 (2022) [5] Y. Litman, E. S. Pos. C. L. Box, R. Martinazzo, R. J. Maurer, and M. Rossi , J. Chem. Phys. 156, 194107 (2022) [6] O. Bridge, R. Martinazzo, S. C. Althorpe, Y. Litman, in preparation (2023)
    Close abstract

    Probing nanocrystal photophysics with spectator excitons

    Date:
    11
    Sunday
    June
    2023
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Sanford Ruhman
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Femtosecond pump-probe experiments on nanocrystals are interpreted primarily in ... Read more Femtosecond pump-probe experiments on nanocrystals are interpreted primarily in terms of state filling of the states involved in the intense band edge absorption features, and bi-exciton shifting which changes the resonance energy of the probe pulse due to presence of pump induced excitations. Results have been interpreted to show 1) that “hot” excitons will relax to the lowest available levels in the conduction band in ~1 ps, and 2) that said intense band edge exciton transition will be bleached linearly with excitons until the underlying states are completely filled. In the talk we describe a new approach involving “spectator excitons” to test these accepted views. It consists of comparing pump-probe experiments on pristine samples, with equivalent scans conducted on the same sample after it has been saturated in cold mono-excitons. We show how this method has uncovered previously unrecognized spin blockades in the relaxation of hot multi-exciton states in CdSe NCs, and simply detects stimulated emission signals even in presence of overlapping absorption. We report specific difficulties of applying this approach on perovskite crystals leading to controversial determination that in quantum confined CsPbBr3 bi-exciton interactions are positive (repulsive) and describe recent time resolved emission data which challenges this result.
    Close abstract

    “How atoms jiggle and wiggle in energy materials”

    Date:
    07
    Wednesday
    June
    2023
    Lecture / Seminar
    Time: 10:30-11:30
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. David Egger
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract:   Energy materials are crystalline, solid-state substances with technological ... Read more   Energy materials are crystalline, solid-state substances with technological applications in energy-conversion or storage devices that include solar cells and batteries. In our work, we are particularly interested in scenarios where these systems show unusual structural dynamical effects. These effects trigger many puzzling questions in regard to updated structure-property relations and improved theoretical understandings of these solids. In my talk, I will present our recent findings regarding theoretical treatments of structural dynamics in energy materials and how we may use them to improve our understanding of their finite-temperature properties. The results will focus on halide perovskite as well as nitride semiconductors and solid-state ion conductors, which we typically investigate in tandem with experiment.
    Close abstract

    Ben May Lecutre Series

    Date:
    01
    Thursday
    June
    2023
    Lecture / Seminar
    Time: 14:00-15:00
    Title: Coherence Maps and State-to-State Pathways of Excitation Energy Transfer
    Location: Stone Administration Building
    Lecturer: Prof Nancy Makri
    Organizer: Ben May Center for Chemical Theory and Computation
    Contact: eli.pollak@weizmann.ac.il
    Abstract: The interplay among electronic coherence, vibrational damping, quantum dispersio ... Read more The interplay among electronic coherence, vibrational damping, quantum dispersion, topological effects and thermal fluctuations leads to rich behaviors in the dynamics of excitation energy flow. We use real-time path integral methods developed in our group to perform fully quantum mechanical simulations of excitation energy transfer in large molecular aggregates. The systems are described through a Frenkel exciton Hamiltonian where all vibrational normal modes of each molecular unit and their coupling to the ground and excited electronic states are treated explicitly at any temperature. Simulations have been carried out in J aggregates of perylene bisimide, model dendrimers, and photosynthetic light harvesting complexes. Coherence maps offer powerful visualization tools that reveal the creation and destruction of quantum superpositions and enable a state-to-state pathway analysis of energy flow.
    Close abstract

    Physics Colloquium

    Date:
    01
    Thursday
    June
    2023
    Colloquium
    Time: 11:15-12:30
    Title: Elastic Strain Engineering for Unprecedented Properties
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Ju Li
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: The emergence of “ultra-strength materials” that can withstand significant f ... Read more The emergence of “ultra-strength materials” that can withstand significant fractions of the ideal strength at component scale without any inelastic relaxation harbingers a new field within mechanics of materials. Recently, we have experimentally achieved more than 13% reversible tensile strains in Si that fundamentally redefines what it means to be Si, and ~7% uniform tensile strain in micron-scale single-crystalline diamond bridge arrays, where thousands of transistors and quantum sensors can be integrated in one diamond microbridge. Elastic Strain Engineering (ESE) aims to endow material structures with very large stresses and stress gradients to guide electronic, photonic, and spin excitations and control energy, mass, and information flows. As “smaller is stronger” for most engineering materials at room temperature, a much larger dynamical range of tensile-and-shear deviatoric stresses for small-scale structures can be achieved, as the defect (e.g., dislocation, crack) population dynamics change from defect-propagation to defect-nucleation controlled. Thus, all six stress components can be used to tune the physical and chemical properties of a material like a 7-element alloy. Four pillars of ESE need to be addressed experimentally and computationally: (a) making materials and structures that can withstand deviatoric elastic strain patterns that are exceptionally large and extended in space-time volume, inhomogeneous, dynamically reversible, or combinations thereof, (b) measuring and understanding how functional properties such as photonic and electronic characteristics vary with imposed elastic strain tensor, (c) characterizing and modeling the mechanisms of stress relaxations; the goal is not to use them for forming but to defeat them at service temperatures (usually room temperature and above) and extended timescales, and (d) computational design based on first principles, e.g. predicting ideal strength surface, topological changes in band structures, etc. assisted by machine learning.
    Close abstract

    Solar Panels for Light-to-Chemical Conversion

    Date:
    29
    Monday
    May
    2023
    Colloquium
    Time: 11:00-12:15
    Title: 2023 G.M.J. SCHMIDT MEMORIAL LECTURE
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Erwin Reisner
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: Solar panels are well known to produce electricity, but they are also in early-s ... Read more Solar panels are well known to produce electricity, but they are also in early-stage development for the production of sustainable fuels and chemicals. These panels mimic plant leaves in shape and function as demonstrated for overall solar water splitting to produce green H2 by the laboratories of Nocera and Domen.1,2 This presentation will give an overview of our recent progress to construct prototype solar panel devices for the conversion of carbon dioxide and solid waste streams into fuels and higher-value chemicals through molecular surface-engineering of solar panels with suitable catalysts. Specifically, a standalone ‘photoelectrochemical leaf’ based on an integrated lead halide perovskite-BiVO4 tandem light absorber architecture has been built for the solar CO2 reduction to produce syngas.3 Syngas is an energy-rich gas mixture containing CO and H2 and currently produced from fossil fuels. The renewable production of syngas may allow for the synthesis of renewable liquid oxygenates and hydrocarbon fuels. Recent advances in the manufacturing have enabled the reduction of material requirements to fabricate such devices and make the leaves sufficiently light weight to even float on water, thereby enabling application on open water sources.4 The tandem design also allows for the integration of biocatalysts and the selective and bias-free conversion of CO2-to-formate has been demonstrated using enzymes.5 The versatility of the integrated leaf architecture has been demonstrated by replacing the perovskite light absorber by BiOI for solar water and CO2 splitting to demonstrate week-long stability.6 An alternative solar carbon capture and utilisation technology is based on co-deposited semiconductor powders on a conducting substrate.2 Modification of these immobilized powders with a molecular catalyst provides us with a photocatalyst sheet that can cleanly produce formic acid from aqueous CO2.7 CO2-fixing bacteria grown on such a ‘photocatalyst sheet’ enable the production of multicarbon products through clean CO2-to-acetate conversion.8 The deposition of a single semiconductor material on glass gives panels for the sunlight-powered conversion plastic and biomass waste into H2 and organic products, thereby allowing for simultaneous waste remediation and fuel production.9 The concept and prospect behind these integrated systems for solar energy conversion,10 related approaches,11 and their relevance to secure and harness sustainable energy supplies in a fossil-fuel free economy will be discussed.
    Close abstract
    Solar Panels for Light-to-Chemical Conversion Colloquium website

    Ultrafast, Nonlinear and Quantum Optics

    Date:
    29
    Monday
    May
    2023
    -
    31
    Wednesday
    May
    2023
    Conference
    Time: 08:00
    Location: The David Lopatie Conference Centre
    Organizer: Department of Physics of Complex Systems,Crown Photonics Center
    Contact: talia.tzahor@weizmann.ac.il
    Ultrafast, Nonlinear and Quantum Optics Conference website

    Magnetic Resonance Seminar: "Quantum sensing of out-of-equilibrium systems with magnetic resonance”

    Date:
    28
    Sunday
    May
    2023
    Lecture / Seminar
    Time: 16:00-17:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Gonzalo A. Alvarez
    Organizer: The Center for Quantum Science and Technology
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Reliable processing of quantum information is crucial for quantum technologies d ... Read more Reliable processing of quantum information is crucial for quantum technologies development. Characterizing the ubiquitous out-of-equilibrium quantum systems [1-3] is essential for designing optimal control and quantum sensing strategies. However, this task is highly challenging due to the complex high-order correlations and non-stationary nature. In this talk, I will present methods to characterize the decoherence of out-of-equilibrium quantum systems [1,4-6]. Using quantum simulations with Solid-State Nuclear Magnetic Resonance, we quantify "out-of-time order correlations" (OTOCs [2-3]) to define a critical threshold in disturbances to achieve reliable control of large quantum systems [1,4-5]. Furthermore, we develop a framework for quantum sensing the dynamics of out-of-equilibrium systems [6]. The sensor manifests spectral and non-Markovian properties, providing a quantum technology to probe time-correlation properties and mitigate the decoherence effects of non-stationary environments. [1] G. A. Alvarez, D. Suter, R. Kaiser. Science 349, 846 (2015). [2] R.J. Lewis-Swan, A. Safavi-Naini, A.M. Kaufman, A.M. Rey. Nat. Rev. Phys. 1, 627 (2019). [3] B. Swingle. Nat. Phys. 14, 988 (2018). [4] F.D. Dominguez, M.C. Rodriguez, R. Kaiser, D. Suter, G.A. Alvarez. Phys. Rev. A 104, 012402 (2021). [5] F.D. Dominguez, G.A. Alvarez. Phys. Rev. A 104, 062406 (2021). [6] M. Kuffer, A. Zwick, G.A. Alvarez. PRX Quantum 3, 020321 (2022).
    Close abstract

    Ultrafast processes and the challenge of decoherence

    Date:
    22
    Monday
    May
    2023
    Colloquium
    Time: 11:00-12:15
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Eberhard K. U. Gross
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: A prominent goal of present-day condensed-matter physics is the design of electr ... Read more A prominent goal of present-day condensed-matter physics is the design of electronic devices with ever faster switching times. As an example I will present the optically induced spin transfer between magnetic sublattices, the so-called OISTR effect, which allows the switching of magnetic textures on the scale of a femto-second or less. This effect was first predicted with real-time TDDFT and later confirmed in many experiments. To create from this effect a real-world device on has to face the problem of decoherence, i.e. the phenomenon that quantum systems tend to lose their quantumness due to interactions with the environment. For electrons, the principal source of decoherence is the non-adiabatic interaction with nuclear degrees of freedom, i.e. with an “environment” that cannot be removed. In fact, the paradigm of electronic-structure theory where electrons move in the static Coulomb potential of clamped nuclei, while useful in the ground state, is an idealization hardly ever satisfied in dynamical processes. Non-adiabaticity, i.e. effects of the coupled motion of electrons and nuclei beyond the Born-Oppenheimer approximation are found everywhere. In this lecture, the exact factorization will be presented as a universal approach to understand and, ultimately, control non-adiabatic effects, in particular decoherence, from an ab-initio perspective.
    Close abstract
    Ultrafast processes and the challenge of decoherence Colloquium website

    Why Can’t We Classically Describe Quantum Systems?

    Date:
    10
    Wednesday
    May
    2023
    Lecture / Seminar
    Time: 13:00-14:00
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Dr. Chinmay Nirkhe
    Organizer: The Center for Quantum Science and Technology
    Contact: rotem.arn@weizmann.ac.il
    Abstract: A central goal of physics is to understand the low-energy solutions of quantum ... Read more A central goal of physics is to understand the low-energy solutions of quantum interactions between particles. This talk will focus on the complexity of describing low-energy solutions; I will show that we can construct quantum systems for which the low-energy solutions are highly complex and unlikely to exhibit succinct classical descriptions. I will discuss the implications these results have for robust entanglement at constant temperature and the quantum PCP conjecture. En route, I will discuss our positive resolution of the No Lowenergy Trivial States (NLTS) conjecture on the existence of robust complex entanglement. Mathematically, for an n-particle system, the low-energy states are the eigenvectors corresponding to small eigenvalues of an exp(n)-sized matrix called the Hamiltonian, which describes the interactions between the particles. Low-energy states can be thought of as approximate solutions to the local Hamiltonian problem with ground-states serving as the exact solutions. In this sense, low-energy states are the quantum generalizations of approximate solutions to satisfiability problems, a central object of study in theoretical computer science. I will discuss the theoretical computer science techniques used to prove circuit lower bounds for all low-energy states. This morally demonstrates the existence of Hamiltonian systems whose entire low-energy subspace is robustly entangled.
    Close abstract

    Physics Colloquium

    Date:
    10
    Wednesday
    May
    2023
    Colloquium
    Time: 11:15-12:00
    Title: GW astrophysics with LIGO/VIRGO data
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Matias Zaldarriaga
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: refreshments at 11:00
    Abstract: I will describe some of our recent work re-analyzing the gravitational wave data ... Read more I will describe some of our recent work re-analyzing the gravitational wave data made public by the LIGO collaboration. More broadly I will discuss some of the outstanding questions related to binary black hole mergers and what the data might be saying about how the GW sources formed. I will comment on some fruitful directions for further improvements.
    Close abstract

    Physics Colloquium

    Date:
    09
    Tuesday
    May
    2023
    Colloquium
    Time: 11:00-12:30
    Title: Intense Laser-Material Interactions: Stars, Exoplanets, and Unique States of Matter in the Laboratory
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Christopher Deeney
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 11:00
    Abstract: Since 1970, the University of Rochester and other laboratories around the world ... Read more Since 1970, the University of Rochester and other laboratories around the world have built more energetic and more powerful lasers. These technology advances have enabled new science regimes. Fifty years later, fusion ignition has been achieved in the laboratory , where more energy than the laser energy was released ; an amazing demonstration of precision science under extreme conditions.Astrophysics is now a laboratory science-new equations of state, constitutive properties and structures are measured at conditions equivalent to giant gas planets and super earths. Ultrashort pulse lasers, a LLE invention acknowledged in the 2018 Nobel Prize for Physics, is enabling ultrahigh field physics and new generations of particle accelerators and light sources. Recent progress on ignition, high-energy-density science and short-pulse laser physics will be summarized. The pursuit of direct-drive fusion and the path to 25 Petawatt lasers will be discussed.
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    08
    Monday
    May
    2023
    Lecture / Seminar
    Time: 11:15-12:45
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is long-standing open question in quantum complexity theory whether the defin ... Read more It is long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (QMA) or if classical witnesses suffice (QCMA). We make progress on this question by constructing a randomized classical oracle separating the respective computational complexity classes. Previous separations [Aaronson-Kuperberg (CCC'07), Fefferman-Kimmel (MFCS'18)] required a quantum unitary oracle. The separating problem is deciding whether a distribution supported on regular un-directed graphs either consists of multiple connected components (yes instance) or consists of one expanding connected component (no instances) where the graph is given in an adjacency-list format by the oracle. Therefore, the oracle is a distribution over n-bit boolean functions.
    Close abstract

    Approaching non-equilibrium: from machine learning to non-adiabatic dynamics

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Sergei Tretiak
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Machine learning (ML) became a premier tool for modeling chemical processes and ... Read more Machine learning (ML) became a premier tool for modeling chemical processes and materials properties. For instance, ML interatomic potentials have become an efficient alternative to computationally expensive quantum chemistry simulations. In the case of reactive chemistry designing high-quality training data sets is crucial to overall model accuracy. To address this challenge, we develop a general reactive ML interatomic potential through unbiased active learning with an atomic configuration sampler inspired by nanoreactor molecular dynamics. The resulting model is then applied to study five distinct condensed-phase reactive chemistry systems: carbon solid-phase nucleation, graphene ring formation from acetylene, biofuel additives, combustion of methane and the spontaneous formation of glycine from early-earth small molecules. In all cases, the results closely match experiment and/or previous studies using traditional model chemistry methods. Altogether, explosive growth of user-friendly ML frameworks, designed for chemistry, demonstrates that the field is evolving towards physics-based models augmented by data science. I will also overview some applications of Non-adiabatic EXcited-state Molecular Dynamics (NEXMD) framework developed at several institutions. The NEXMD code is able to simulate tens of picoseconds photoinduced dynamics in large molecular systems. As an application, I will exemplify ultrafast coherent excitonic dynamics guided by intermolecular conical intersections. Here X-ray Raman signals are able to sensitively monitor the coherence evolution. The observed coherences have vibronic nature that survives multiple conical intersection passages for several hundred femtoseconds at room temperature. These spectroscopic signals are possible to measure at XFEL facilities and our modeling results allow us to understand and potentially manipulate excited state dynamics and energy transfer pathways toward optoelectronic applications. References: 1. N. Fedik, R. Zubatyuk, N. Lubbers, J. S. Smith, B. Nebgen, R. Messerly, Y. W. Li, M. Kulichenko, A. I. Boldyrev, K. Barros, O. Isayev, and S. Tretiak “Extending machine learning beyond interatomic potentials for predicting molecular properties” Nature Rev. Chem. 6, 653 (2022). 2. G. Zhou, N. Lubbers, K. Barros, S. Tretiak, B. Nebgen, “Deep Learning of Dynamically Responsive Chemical Hamiltonians with Semi-Empirical Quantum Mechanics,” Proc. Nat. Acad. Sci. USA, 119 e2120333119 (2022) 3. S. Zhang, M. Z. Makos, R. B. Jadrich, E. Kraka, B. T. Nebgen, S. Tretiak, O. Isayev, N. Lubbers, R. A. Messerly, and J. S. Smith “Exploring the frontiers of chemistry with a general reactive machine learning potential,” (2023) https://chemrxiv.org/engage/chemrxiv/article-details/6362d132ca86b84c77ce166c 4. A. De Sio, E. Sommer, X. T. Nguyen, L. Gross, D. Popović, B. Nebgen, S. Fernandez-Alberti, S. Pittalis, C. A. Rozzi, E. Molinari, E. Mena-Osteritz, P. Bäuerle, T. Frauenheim, S. Tretiak, C. Lienau, “Intermolecular conical intersections in molecular aggregates” Nature Nanotech. 16, 63 – 68 (2021). 5. V. M. Freixas, D. Keefer, S. Tretiak, S. Fernandez-Alberti, and S. Mukamel, “Ultrafast coherent photoexcited dynamics in a trimeric dendrimer probed by X-ray stimulated-Raman signals,” Chem. Sci., 13, 6373 – 6384 (2022).
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-13:00
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-13:00
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-13:00
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-12:45
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-12:30
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-12:30
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Foundations of Computer Science Seminar

    Date:
    24
    Monday
    April
    2023
    Lecture / Seminar
    Time: 11:15-12:45
    Title: A distribution testing oracle separation between QMA and QCMA
    Location: Jacob Ziskind Building
    Lecturer: Chinmay Nirkhe
    Organizer: Department of Computer Science and Applied Mathematics
    Contact: karina.avadia@weizmann.ac.il
    Abstract: It is a long-standing open question in quantum complexity theory whether the def ... Read more It is a long-standing open question in quantum complexity theory whether the definition of non-deterministic quantum computation requires quantum witnesses (
    Close abstract

    Quantum computing with trapped ions

    Date:
    17
    Monday
    April
    2023
    Lecture / Seminar
    Time: 13:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Ferdinand Schmidt-Kaler (QUANTUM, Johannes Gutenberg Universität Mainz)
    Organizer: The Center for Quantum Science and Technology
    Contact: eti.shalem@weizmann.ac.il
    Details: Falafel at 12:45
    Abstract: Quantum technologies allow for fully novel schemes of hybrid computing. We empl ... Read more Quantum technologies allow for fully novel schemes of hybrid computing. We employ modern segmented ion traps. I will sketch architectures, the required trap technologies and fabrication methods, control electronics for quantum register reconfigurations, and recent improvements of qubit coherence and gate performance. Currently gate fidelities of 99.995% (single bit) and 99.8% (two bit) are reached. We are implementing a reconfigurable qubit register and have realized multi-qubit entanglement [1] and fault-tolerant syndrome readout [2] in view for topological quantum error correction [3] and realize user access to quantum computing [4]. The setup allows for mid-circuit measurements and real-time control of the algorithm. We are currently investigating various used cases, including variational quantum eigensolver approaches for chemistry or high energy relevant models, and measurement-based quantum computing. The fully equipped in house clean room facilities for selective laser etching of glass enables us to design and fabricate complex ion trap devices, in order to scale up the number of fully connected qubits. Also, we aim for improving on the speed of entanglement generation. The unique and exotic properties of ions in Rydberg states [5] are explored experimentally, staring with spectroscopy [6] of nS and nD states where states with principal quantum number n=65 are observed. The high polarizability [7] of such Rydberg ions should enable sub-μs gate times [8]. [1] Kaufmann er al, Phys. Rev. Lett. 119, 150503 (2017) [2] Hilder, et al., Phys. Rev. X.12.011032 (2022) [3] Bermudez, et al, Phys. Rev. X 7, 041061 (2017) [4] https://iquan.physik.uni-mainz.de/ [5] A. Mokhberi, M. Hennrich, F. Schmidt-Kaler, Trapped Rydberg ions: a new platform for quantum information processing, Advances In Atomic, Molecular, and Optical Physics, Academic Press, Ch. 4, 69 (2020), arXiv:2003.08891 [6] Andrijauskas et al, Phys. Rev. Lett. 127, 203001 (2021) [7] Niederlander et al, NJP 25 033020 (2023) [8] Vogel et al, Phys. Rev. Lett. 123, 153603 (2019)
    Close abstract

    Polymorphous networks of intrinsic local motifs in crystals

    Date:
    17
    Monday
    April
    2023
    Colloquium
    Time: 11:00-12:15
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Alex Zunger
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: Predicting properties of crystals and molecules via quantum theory of matter gen ... Read more Predicting properties of crystals and molecules via quantum theory of matter generally requires knowing (A) the nature of electronic interactions in the system, and (B) where atoms and various moments are (“structure”). Some of the historical failures to predict basic effects in ‘Quantum Materials’ were often tracked back to the need to improve our understanding of (A), such as accounting for ‘strong electron correlation’. Examples include Mott insulators; mass enhancement in superconductors; metal-insulator transitions in oxides, or even the quantitative underestimation of predicted band gaps of cubic Halide Perovskites. This talk explores a different resolution of the aforementioned conflicts with experiment in terms of hidden structure (B) above. This include configurations of magnetic moments or electric dipole moments, not only in the ordered ground states, but also in paramagnetic and paraelectric phases, and in nonmagnetic cubic phases of halide perovskites, all considered previously to be ‘featureless phases. Importantly, such ‘Quantum Texture’ can be predicted theoretically by minimization of the constrained internal energy, even before temperature sets in. It thus represents intrinsic tendencies to lower energy by breaking symmetry. Using such polymorphous networks in band theory explains Mott physics without correlation as well as Halide Perovskites before dynamics. This highlights the importance of experimental observation of distributions of local symmetries, distinct from the global average crystallographic symmetries.
    Close abstract
    Polymorphous networks of intrinsic local motifs in crystals Colloquium website

    Chemical and Biological Physics Guest Seminar

    Date:
    02
    Sunday
    April
    2023
    Lecture / Seminar
    Time: 14:00
    Title: Ab initio approaches to nonequilibrium dynamics and molecular quantum systems
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof Prineha Narang
    Organizer: Department of Chemical and Biological Physics
    Contact: Gilad.haran@weizmann.ac.il
    Abstract: In this talk, I will present theoretical and computational chemistry approaches ... Read more In this talk, I will present theoretical and computational chemistry approaches to describe excited-states in quantum matter, and predicting emergent states created by external drives. Understanding the role of such light-matter interactions in the regime of correlated electronic systems is of paramount importance to fields of study across chemical and condensed matter physics, and ultrafast dynamics1. The simultaneous contribution of processes that occur on many time and length-scales have remained elusive for state-of-the-art calculations and model Hamiltonian approaches alike, necessitating the development of new methods in computational chemistry. I will discuss our work at the intersection of ab initio cavity quantum-electrodynamics and electronic structure methods to treat electrons, photons and phonons on the same quantized footing, accessing new observables in strong light-matter coupling. Current approximations in the field almost exclusively focus on electronic excitations, neglecting electron-photon effects, for example, thereby limiting the applicability of conventional methods in the study of polaritonic systems, which requires understanding the coupled dynamics of electronic spins, nuclei, phonons and photons. With our approach we can access correlated electron-photon and photon-phonon dynamics2–7, essential to our latest work on driving quantum materials far out-of-equilibrium to control the coupled electronic and vibrational degrees-of-freedom 8–19. In the second part of my talk, I will demonstrate how the same approach can be generalized in the context of control of molecular quantum matter and quantum transduction. As a first example, I will discuss a cavity-mediated approach to break the inversion symmetry allowing for highly tunable even-order harmonic generation (e.g. second- and fourth-harmonic generation) naturally forbidden in such systems. This relies on a quantized treatment of the coupled light-matter system, similar to the driven case, where the molecular matter is confined within an electromagnetic environment and the incident (pump) field is treated as a quantized field in a coherent state. When the light-molecule system is strongly coupled, it leads to two important features: (i) a controllable strong-coupling-induced symmetry breaking, and (ii) a tunable and highly efficient nonlinear conversion efficiency of the harmonic generation processes 20–22. Both of these have implications for molecular quantum architectures. Being able to control molecules at a quantum level gives us access to degrees of freedom such as the vibrational or rotational degrees to the internal state structure. Finally, I will give an outlook on connecting ideas in cavity control of molecules with quantum information science.
    Close abstract

    Chemical and Biological Physics Guest Seminar

    Date:
    23
    Thursday
    March
    2023
    Lecture / Seminar
    Time: 10:00-11:00
    Title: Building and testing semiclassical models for molecular plasmonics
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof Maxim Sukharev
    Organizer: Department of Chemical and Biological Physics
    Contact: Gilad.haran@weizmann.ac.il
    Abstract: Molecular plasmonics has been a hot topic for the past several years. At the hea ... Read more Molecular plasmonics has been a hot topic for the past several years. At the heart of the primary interest in plasmonics is the strong electromagnetic field localization at resonant frequencies corresponding to surface plasmon-polariton modes. Thanks to riveting advancements in nanofabrication technologies, we have achieved nearly 1 nm spatial resolution (and in some cases even below that!) and are able to fabricate a wide variety of nanosystems ranging from nanoparticles of various shapes to metasurfaces comprised of periodic arrays of nanoparticles and/or nanoholes of any imaginable geometry. Such systems have recently emerged as new platforms for strong light-matter interactions. Combined with molecular ensembles, these constructs exhibit a remarkable set of optical phenomena ranging from the exciton-plasmon strong coupling to the second harmonic generation altered by molecular resonances. In this talk I will discuss both linear and nonlinear optical properties of plasmonic materials coupled to quantum emitters of various complexity. I will also introduce a newly developed computational approach that can be used to efficiently simulate a large number of complex molecules driven by electromagnetic radiation crafted at plasmonic interfaces.
    Close abstract

    The platypus of the quantum channel zoo

    Date:
    13
    Monday
    March
    2023
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Prof. Felix Leditzky
    Organizer: The Center for Quantum Science and Technology
    Contact: eti.shalem@weizmann.ac.il
    Abstract: Understanding quantum channels and the strange behavior of their capacities is a ... Read more Understanding quantum channels and the strange behavior of their capacities is a key driver of quantum information theory. Despite having rigorous coding theorems, quantum capacities are poorly understood due to super-additivity effects. We will talk about a remarkably simple, low-dimensional, single-parameter family of quantum channels with exotic quantum information-theoretic features. As the simplest example from this family, we focus on a qutrit-to-qutrit channel that is intuitively obtained by hybridizing together a simple degradable channel and a completely useless qubit channel. Such hybridizing makes this channel's capacities behave in a variety of interesting ways. For instance, the private and classical capacity of this channel coincide and can be explicitly calculated, even though the channel does not belong to any class for which the underlying information quantities are known to be additive. Moreover, the quantum capacity of the channel can be computed explicitly, given a clear and compelling conjecture is true. This "spin alignment conjecture," which may be of independent interest, is proved in certain special cases and additional numerical evidence for its validity is provided. We further show that this qutrit channel demonstrates superadditivity when transmitting quantum information jointly with a variety of assisting channels, in a manner unknown before. A higher-dimensional variant of this qutrit channel displays super-additivity of quantum capacity together with an erasure channel. Subject to the spin-alignment conjecture, our results on super-additivity of quantum capacity extend to lower-dimensional channels as well as larger parameter ranges. In particular, super-additivity occurs between two weakly additive channels each with large capacity on their own, in stark contrast to previous results. Remarkably, a single, novel transmission strategy achieves super-additivity in all examples. Our results show that super-additivity is much more prevalent than previously thought. It can occur across a wide variety of channels, even when both participating channels have large quantum capacity. This is joint work with Debbie Leung, Vikesh Siddhu, Graeme Smith, and John Smolin, and based on the papers https://arxiv.org/abs/2202.08380 and https://arxiv.org/abs/2202.08377.
    Close abstract

    Tensor networks, fundamental theorems, and complexity

    Date:
    06
    Monday
    March
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Prof. Michael Walter
    Organizer: The Center for Quantum Science and Technology
    Contact: eti.shalem@weizmann.ac.il
    Abstract: Tensor networks describe high-dimensional tensors succinctly, in terms of a netw ... Read more Tensor networks describe high-dimensional tensors succinctly, in terms of a network or graph of local data. Many interesting tensors arise in this way -- from many-body quantum states in physics to the matrix multiplication tensors in algebraic complexity. While widely successful, the structure of tensor networks is still only partially understood. In this talk, I will give a gentle introduction to tensor networks and explain some recent advances in their theory. In particular, we will discuss the significance of the so-called “fundamental theorem”, which is at the heart of much of the success of tensor networks, and explain how to generalize it to higher dimensions. Before our work, "no go" results suggested that such a generalization might not exist!! Along the way, we will see how to turn an undecidable problem into one that admits an algorithmic solution. To achieve this we draw on recent progress in theoretical computer science and geometric invariant theory.
    Close abstract

    Strong light-exciton interactions in 2D semiconductors

    Date:
    22
    Wednesday
    February
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Itai Epstein
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: The remarkable properties of excitons in transition-metal-dichalcogenides (TMDs) ... Read more The remarkable properties of excitons in transition-metal-dichalcogenides (TMDs), together with the ability to readily control their charge carriers, have attracted a significant amount of interest in recent years. Despite the atomic dimensions of the hosting 2D semiconductors, TMD excitons exhibit strong interaction with light, both in absorption and photoemission processes, and practically dominate the optical response of these 2D materials. In this talk, I will introduce several approaches for achieving extremely strong light-exciton interactions. First, by optical and electrical manipulation of TMD excitons inside a van der Waals heterostructure cavity [1], second, via the formation of highly-confined, in-plane exciton polaritons [2], and third, through the realization of valley-polarized hyperbolic exciton polaritons [3]. These enhanced light–exciton interactions may provide a platform for studying excitonic phase-transitions, quantum nonlinearities and the enablement of new possibilities for 2D semiconductor-based optoelectronic devices. [1] I. Epstein et al, "Near-unity Light Absorption in a Monolayer WS2 Van der Waals Heterostructure Cavity", Nano letters 20 (5), 3545-3552 (2020). [2] I. Epstein et al, "Highly Confined In-plane Propagating Exciton-Polaritons on Monolayer Semiconductors", 2D Materials 7, 035031 (2020). [3] T. Eini, T. Asherov, Y. Mazor, and I. Epstein, "Valley-polarized Hyperbolic Exciton Polaritons in Multilayer 2D Semiconductors at Visible Frequencies", Phys. Rev. B 106, L201405 (2022).
    Close abstract

    Physics Colloquium

    Date:
    19
    Sunday
    February
    2023
    Colloquium
    Time: 11:15-12:30
    Title: New Avenues in Quantum Computing: Beyond Quantum Circuits with Trapped-Ion Qubits
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Or Katz
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more
    Abstract: Trapped ions are a leading quantum technology for quantum computation and simula ... Read more Trapped ions are a leading quantum technology for quantum computation and simulation, with the capability to solve computationally hard problems and deepen our understanding of complex quantum systems. The quantum circuit model is the central paradigm for quantum computation, enabling the realization of various quantum algorithms by application of multiple one- and two-qubit entangling operations. However, the typical number of entangling operations required by this model increases exponentially with the number of qubits, making it difficult to apply to many problems. In my presentation, I will discuss new methods for realizing quantum gates and simulations that go beyond the quantum circuit model. I will first describe a single-step protocol for generating native, -body interactions between trapped-ion spins, using spin-dependent squeezing. Next, I will present a preparation of novel phases of matter using simultaneous and reconfigurable spin-spin interactions. Lastly, I will explore new avenues to harness the long-lived phonon modes in trapped-ion crystals for simulating complex bosonic and spin-boson models that are difficult to solve using classical methods. The presented techniques could push the performance of trapped-ion systems to solve problems that are currently beyond their reach.
    Close abstract

    Physics Colloquium

    Date:
    02
    Thursday
    February
    2023
    Colloquium
    Time: 11:15-12:30
    Title: Quantum materials by design
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Cory Dean
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - coffee, tea and more...
    Abstract: The electronic properties of a material are dictated by both the composition and ... Read more The electronic properties of a material are dictated by both the composition and arrangement of its atomic lattice. Combining elemental atoms selected from the periodic table in principle provides for infinite variety of materials to be realized. However, thermodynamic constraints limit which atoms may bond into which symmetry classes; materials may or may not be air sensitive; synthesis conditions may be impractical; impurities and defects may substantially obscure intrinsic electronic properties; and the resulting electron behaviour may not be predictive owing to phenomena such as strong electron interactions, spontaneous magnetic ordering, fermi-surface reconstruction or other effects not captured by single-particle band-structure calculations. In this talk, I will explore new approaches to synthesizing quantum materials by augmenting the atomic lattice structure in 2D materials with a superimposed superlattice potential. Artificially engineering lattice potentials provide opportunities to synthesize materials beyond the periodic table, with the ultimate promise to be able to realize and manipulate arbitrary electronic states, by design. Opportunities and challenges, in this exciting new field will be reviewed, and the prospects for quantum simulation in a solid-state platform will be discussed.
    Close abstract

    M.Sc thesis defense: “Fermi-polaron description of excitonic scattering processes in layered systems from first principles”

    Date:
    01
    Wednesday
    February
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Guy Voscoboynik
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Layered materials exhibit unique charge and energy transfer characteristics, mak ... Read more Layered materials exhibit unique charge and energy transfer characteristics, making them promising candidates for emerging photophysical and photochemical applications, and particularly in energy conversion and quantum information science. In two-dimensional systems, spatial confinement in a certain dimension causes reduced dielectric screening and enhanced Coulomb interaction compared to bulk materials. Upon light excitation, the relaxation processes of the charge and energy carriers, as well as their rearrangement in the lateral plane, allow for unique and structure-specific interaction dynamics of the electrons and holes in these systems and of their bound states - neutral and charged excitons. In particular, these dimensionality effects induce strong exciton-electron and exciton-hole interactions in doped or gated systems, where optical excitations coexist alongside electronic excitations. These interactions dominate the exciton decay and diffusion and introduce bound three-particle states in such systems. A many-particle theoretical picture of the formation and propagation of these states is crucial for proper tracking and understanding of the interaction pathways, crystal momentum effects, the involved particle-particle coupling and their relation to the underlying structure, dimensionality, and symmetry.
    Close abstract

    "Molecules in a Quantum-Optical Flask"

    Date:
    25
    Wednesday
    January
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Tal Schwartz
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: "Molecules in a Quantum-Optical Flask" When confined to small dimensions, the ... Read more "Molecules in a Quantum-Optical Flask" When confined to small dimensions, the interaction between light and matter can be enhanced up to the point where it overcomes all the incoherent, dissipative processes. In this "strong coupling" regime the photons and the material start to behave as a single entity, having its own quantum states and energy levels. In this talk I will discuss how such cavity-QED effects can be used in order to control material properties and molecular processes. This includes, for example, modifying photochemical reactions [1], enhancing excitonic transport up to ballistic motion close to the light-speed [2-3] and potentially tailoring the mesoscopic properties of organic crystals, by hybridizing intermolecular vibrations with electromagnetic THz fields [4-5]. 1. J. A. Hutchison, T. Schwartz, C. Genet, E. Devaux, and T. W. Ebbesen, "Modifying Chemical Landscapes by Coupling to Vacuum Fields," Angew. Chemie Int. Ed. 51, 1592 (2012). 2. G. G. Rozenman, K. Akulov, A. Golombek, and T. Schwartz, "Long-Range Transport of Organic Exciton-Polaritons Revealed by Ultrafast Microscopy," ACS Photonics 5, 105 (2018). 3. M. Balasubrahmaniyam, A. Simkovich, A. Golombek, G. Ankonina, and T. Schwartz, "Unveiling the mixed nature of polaritonic transport: From enhanced diffusion to ballistic motion approaching the speed of light," arXiv:2205.06683 (2022). 4. R. Damari, O. Weinberg, D. Krotkov, N. Demina, K. Akulov, A. Golombek, T. Schwartz, and S. Fleischer, "Strong coupling of collective intermolecular vibrations in organic materials at terahertz frequencies," Nat. Commun. 10, 3248 (2019). 5. M. Kaeek, R. Damari, M. Roth, S. Fleischer, and T. Schwartz, "Strong Coupling in a Self-Coupled Terahertz Photonic Crystal," ACS Photonics 8, 1881 (2021).
    Close abstract

    Magnetism and spin squeezing with arrays of Rydberg atoms

    Date:
    22
    Sunday
    January
    2023
    Lecture / Seminar
    Time: 11:00-13:00
    Title: Magnetism and spin squeezing with arrays of Rydberg atoms
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Antoine Browaeys
    Organizer: The Center for Quantum Science and Technology
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 10:30
    Abstract: This talk will present our recent work on the use of arrays of Rydberg atoms to ... Read more This talk will present our recent work on the use of arrays of Rydberg atoms to study quantum magnetism and to generate entangled states useful for quantum metrology. We rely on laser-cooled ensembles of up to hundred individual atoms trapped in microscopic optical tweezer arrays. By exciting the atoms into Rydberg states, we make them interact by the resonant dipole interaction. The system thus implements the XY spin ½ model, which exhibits various magnetic orders depending on the ferromagnetic or antiferromagnetic nature of the interaction. In particular, we adiabatically prepare long-range ferromagnetic order. When the system is placed out of equilibrium, the interactions generate spin squeezing. We characterize the degree of squeezing and observe that it scales with the number of atoms.
    Close abstract

    Collective light scattering in cold atomic ensembles: super-radiance & driven Dicke model

    Date:
    19
    Thursday
    January
    2023
    Lecture / Seminar
    Time: 16:00-18:00
    Title: Collective light scattering in cold atomic ensembles: super-radiance & driven Dicke model
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Antoine Browaeys
    Organizer: The Center for Quantum Science and Technology
    Contact: eti.shalem@weizmann.ac.il
    Details: Refreshments at 15:30
    Abstract: This talk will present our recent work on the observation of super-radiance in a ... Read more This talk will present our recent work on the observation of super-radiance in a cloud of cold atoms and the implementation of the driven Dicke model in free space. We start from an elongated cloud of laser cooled atoms that we excite either perpendicularly or along its main axis. This situation bears some similarities with cavity quantum electrodynamics: here the cavity mode is replaced by the diffraction mode of the elongated cloud. We observe superradiant pulses of light after population inversion. When exciting the cloud along the main axis, we observe the Dicke super-radiant phase transition predicted 40 years ago and never observed in free space. We also measure the statistics of the emitted light and find that it has the properties predicted for a super-radiant laser.
    Close abstract

    Special Physics Colloquium

    Date:
    10
    Tuesday
    January
    2023
    Colloquium
    Time: 16:15-18:00
    Title: Quantum Simulation: from many to few body problems.
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Ignacio Cirac
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 15:45- Coffee, tea and Refreshments
    Abstract: Many-body quantum systems are very difficult to simulate with classical computer ... Read more Many-body quantum systems are very difficult to simulate with classical computers, as the computational resources (time and memory) usually grow exponentially with the size of the system. However, quantum computers and analog quantum simulators can perform that task much more efficiently. In this talk, I will first review some of the quantum algorithms that have been proposed to simulate dynamics, prepare ground states, or compute physical properties at finite temperatures. I will then focus on analog quantum simulation with cold atoms in optical lattices and describe methods for tackling physics and chemistry problems with such a system.
    Close abstract

    Quantum metrology for various applications and platforms

    Date:
    09
    Monday
    January
    2023
    Lecture / Seminar
    Time: 14:30-15:30
    Location: Maurice and Gabriela Goldschleger Center For Nanophysics
    Lecturer: Dr. Tuvia Gefen (Caltech)
    Organizer: The Center for Quantum Science and Technology
    Contact: rotem.arn@weizmann.ac.il
    Abstract: The field of quantum metrology seeks to develop quantum protocols to enhance the ... Read more The field of quantum metrology seeks to develop quantum protocols to enhance the precision of measurements with applications ranging from NMR and gravimeters to calibration of quantum devices. The general tools and bounds of quantum metrology assume perfect detection. However, the detection in most quantum experimental platforms is noisy and imperfect. We fill this gap and develop a theory that takes into account general measurements . We generalize the precision bounds to account for arbitrary detection channels. We find the general form of the precision bounds and of the optimal control for pure states. We then consider quantum states in a multi-partite system and study the impact of detection noise on quantum enhancement in sensitivity. Interestingly, the achievable sensitivity depends crucially on the allowed control operations. For local optimal control, the detection noise severely degrades the sensitivity and limits any quantum enhancement to a constant factor. On the other hand, with optimal global control the detection noise can be completely removed, and the noiseless sensitivity bounds can be retrieved for a generic class of quantum states (including all pure states and symmetric states).
    Close abstract

    Physics Hybrid Colloquium

    Date:
    22
    Thursday
    December
    2022
    Colloquium
    Time: 11:15-12:30
    Title: New Astrophysical Puzzles from Studies of Low Mass Galaxies beyond the Milky Way
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Shani Danieli
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - coffee, tea and more...
    Abstract: Low-mass galaxies provide an essential testing ground for theoretical prediction ... Read more Low-mass galaxies provide an essential testing ground for theoretical predictions of cosmology. Their number densities, structures, and internal dynamics provide some of the most interesting clues to the nature of dark matter and the theory of galaxy formation on small scales. Recent advances in telescope instrumentation and image analysis techniques have enabled comprehensive investigations of such low surface brightness galaxies. I will present results from novel observations of low-mass galaxies beyond our local galactic neighborhood, uncovering their significant diverseness and new astrophysical puzzles. I will discuss some of the follow-up observations of these extragalactic low-mass galaxies, focusing on their dark matter content and intriguing globular cluster populations. I will conclude by briefly discussing ongoing and future surveys that collectively have the potential to unveil the physics of dark matter.
    Close abstract

    Chemical and Biological Physics Guest Seminar

    Date:
    21
    Wednesday
    December
    2022
    Lecture / Seminar
    Time: 15:00
    Title: Quantum simulations and interfaces with Rydberg atoms
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof David Petrosyan
    Organizer: Department of Chemical and Biological Physics
    Contact: gershon.kurizki@weizmann.ac.il
    Abstract: Atoms in the highly excited Rydberg states possess unique properties, including ... Read more Atoms in the highly excited Rydberg states possess unique properties, including long lifetimes and huge dipole moments, which facilitate their use in various quantum technology applications. I will discuss recent progress in quantum simulations of many-body physics with strongly-interacting Rydberg atoms and coherent interfaces of Rydberg atoms with superconducting microwave resonators and optical photons, and present some of our results in this research.
    Close abstract

    Israel Quantum Information Theory Day

    Date:
    21
    Wednesday
    December
    2022
    Lecture / Seminar
    Time: 09:30
    Location: The David Lopatie Conference Centre
    Organizer: The Center for Quantum Science and Technology
    Abstract: The Israel Quantum Information Theory day brings together researchers, postdocto ... Read more The Israel Quantum Information Theory day brings together researchers, postdoctoral scholars and Ph.D. students from Israel working on the theory of quantum computation and information processing for a day of scientific talks, research discussions and social interaction. Registration: https://tinyurl.com/2rxsuykb
    Close abstract
    Israel Quantum Information Theory Day Lecture / Seminar website

    From atomic imaging and functionalizing of inorganic 2D materials to molecular imaging of organic 2D materials

    Date:
    18
    Sunday
    December
    2022
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Ute Kaiser
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: In this lecture, the theoretical and technical base for atomic imaging of defect ... Read more In this lecture, the theoretical and technical base for atomic imaging of defects in inorganic 2D materials in the low-voltage transmission electron microscope SALVE will be discussed. Atomic defects can significantly change the properties of the material: Using 2D-TMDs and 2D-TMPTs and corresponding heterostructures, this is shown experimentally and verified by corresponding quantum mechanical calculations. We also use the electron beam for the targeted formation of new phases in the inorganic 2D matrix. Since the interaction cross-sections of electron beam and organic 2D materials differ strongly from the inorganic case, we explore highest-resolution imaging conditions for 2D polymers and various 2D MOFs and show that there is a trend towards lower voltage TEM as well. We may conclude that low-voltage TEM and low-dimensional materials are just made for each other.
    Close abstract

    Origin of compact exoplanetary systems

    Date:
    04
    Sunday
    December
    2022
    Lecture / Seminar
    Time: 15:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Raluca Rufu SwRI, Boulder
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: One of the most surprising discoveries in exoplanet science has been the existen ... Read more One of the most surprising discoveries in exoplanet science has been the existence of compact systems of Earth to super-Earth sized planets. These multi-planet systems have nearly circular, coplanar orbits located at distances of only ∼ 0.01 − 0.1 AU, a region devoid of planets in our Solar System. Although compact systems comprise a large fraction of known exoplanetary systems, their origin remains debated. Common to all prior models of compact system origin is the assumption that infall to the stellar disk ends before planets form. However, there is growing observational, theoretical, and meteoritical evidence of the early growth of mm-sized “pebbles” during the infall phase. We propose that accretion of compact systems occurs during stellar infall. As a cloud core collapses, solids are gradually accumulated in the disk, producing favorable conditions for the formation and survival of close-in planets. A key feature of this model is that the reduced gas-to-solids ratio in the planet accretion region can allow for the formation and survival of compact systems, even with Type-I migration. Accretion within infall-supplied disks has been studied in the context of gas planet satellite origin. Formation models predict that the total mass of the satellite system during this evolution maintains a nearly constant mass ratio ∼10^−4 compared to the host planet’s mass. The maximum mass ratio of compact exoplanetary systems compared to the stellar mass are similar to those of the giant satellite system, suggesting that accretion of compact systems may be similar to regular satellite formation.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    24
    Thursday
    November
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Fractionalized quantum states of matter through the duality lens
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. David Mross
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - coffee, tea and more...
    Abstract: The building blocks of condensed matter systems are just humble electrons. Still ... Read more The building blocks of condensed matter systems are just humble electrons. Still, their excitations may carry fractional quantum numbers or obey exchange statistics that are neither bosonic nor fermionic. An essential question is how to ‘get fractions by combining integers’ and what prompts a microscopic system to do so. I will introduce the basic mechanism behind such fractionalization and describe two examples where it arises in nature. The first is the fractional quantum Hall effect, where I will explain how topologically protected neutral modes can be detected via pure charge-conductance measurements. I will then discuss the phenomenon of spin-charge separation and use field-theoretic dualities to construct concrete models where it occurs.
    Close abstract

    The Role of Active Encapsulation in Perovskite Solar Cells

    Date:
    23
    Wednesday
    November
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Shaibal Sarkar
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: From a perovskite photovoltaic device standpoint, the Al2O3 ALD can be thought o ... Read more From a perovskite photovoltaic device standpoint, the Al2O3 ALD can be thought of as a thin film encapsulate to protect the underlined material from the extrinsic entities. However, as per the literature is concerned, the role of Al2O3 ALD in the perovskite photovoltaic devices is much beyond a mare passive component. This raises a severe ambiguity over the choice of surface (or interface) on which ALD needs to be done for optimized device performance, in terms of the device efficiency and stability. In my presentation, I would like to elucidate the characteristic differences between the surface limited and substrate enhanced ALD processes which is important to perovskite devices. The objective here is to discuss a unified correlation between the role of the Al2O3 ALD mechanism with the perovskite device performance by excluding popular overestimated assumption about the conformality on non-ideal surface, like perovskite or organic thin films. In addition, I would like to emphasize on the fact that how the ALD process can be used to passivate the buried interfacial defect and enhancing the VOC, PL and ELQE.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    17
    Thursday
    November
    2022
    Colloquium
    Time: 11:15-12:30
    Title: : All known Type Ia supernova models fail to reproduce the observed luminosity-width correlation
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Doron Kushnir
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: Type Ia supernovae are fundamental phenomena in nature. They are one of the lead ... Read more Type Ia supernovae are fundamental phenomena in nature. They are one of the leading distributors of heavy chemical elements and, in some cases, important production sites (e.g., iron). Type Ia supernovae are very homogenous and bright, allowing their distance to be measured on cosmological scales. In recent years, measurements of Type Ia supernovae have led to the discovery that the universe's expansion is accelerating, suggesting the existence of dark energy. Type Ia supernovae are likely thermonuclear explosions of white-dwarf stars, which are sufficiently dense to allow explosive thermonuclear burning if adequately ignited. However, a robust comparison of theoretical scenarios for the progenitor systems to observations is challenging due to the inability to accurately calculate the dynamics of the explosion and the emitted radiation. We have developed novel observational and numerical methods by exploiting the physical principles behind Type Ia supernovae. The new observational techniques allow the derivation of a specific luminosity-width correlation that does not require radiation transfer calculations for comparison. The new numerical methods allow for the first time to calculate this luminosity-width correlation with a percent accuracy for multidimensional progenitor scenarios with current computational facilities. We show that all known Type Ia supernova models fail to reproduce the observed luminosity-width correlation.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    03
    Thursday
    November
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Opening up the Gravitational Wave Spectrum
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Surjeet Rajendran
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: The historic discovery of gravitational waves by LIGO has initiated a new era of ... Read more The historic discovery of gravitational waves by LIGO has initiated a new era of astronomy, permitting us to observe the universe through new eyes. LIGO is sensitive to gravitational waves at frequencies above 40 Hz. Much like the case of electromagnetism, there is a strong science case to observationally probe other parts of the gravitational wave spectrum. Significant advances on this front have been made in the mHz band by the LISA collaboration and the nHz range by the NanoGRAV collaboration. How might be probe other gravitational wave frequencies? In this talk, I will discuss the use of atom interferometers to probe gravitational waves in the 1 Hz band. I will also explore the potential use of asteroids as test masses to detect gravitational waves at micro Hz frequencies and the possible use of astrometry in the nHz - micro Hz regime.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    22
    Thursday
    September
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Dipolar quantum droplets and supersolids
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Dr. Tilman Pfau
    Organizer: Faculty of Physics
    Contact: eti.shalem@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: Dipolar interactions are fundamentally different from the usual van der Waals fo ... Read more Dipolar interactions are fundamentally different from the usual van der Waals forces in real gases. Besides its anisotropy the dipolar interaction is nonlocal and as such allows for self organized structure formation, like in many different fields of physics. Although the bosonic dipolar quantum liquid is very dilute, stable droplets and supersolids as well as honeycomb or labyrinth patterns can be formed due to the presence of quantum fluctuations beyond the mean field theory.
    Close abstract

    Chemical and Biological Physics Guest Seminar

    Date:
    04
    Thursday
    August
    2022
    Lecture / Seminar
    Time: 11:00
    Title: Exciton-carrier mixtures in monolayer semiconductors
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Alexey Chernikov
    Organizer: Department of Chemical and Biological Physics
    Contact: terry.debesh@weizmann.ac.il
    Abstract: Coexistence of optical and electrical excitations in semiconductors has a long h ... Read more Coexistence of optical and electrical excitations in semiconductors has a long history of research. This scenario typically involves simultaneous presence of Coulomb-bound electron-hole pairs, known as excitons, and free charge carriers. Conceptually similar to related phenomena in the ultra cold atom gases, exciton-carrier mixtures strongly influence the properties of excited semiconductors and their response to external fields. It involves the formation of bound three-particle states known as charged excitons or trions, Fermi polarons, renormalization and screening effects, as well as the Mott-transition in the high-density regime. These phenomena offer fertile ground to merge the realms of optics and transport, motivated by the availability of excitations that are both electrically tunable and couple strongly to light. Van der Waals monolayer semiconductors and layered metal-halide perovskites recently emerged as particularly suitable platforms to study exciton-carrier mixtures due to exceptionally strong Coulomb interactions on the order of many 100’s of meV. In this talk, I will discuss a number of intriguing phenomena associated with coupling of excitons to free charge carriers in these systems. I will present experimental evidence for dressing of excited exciton states by continuously tunable Fermi sea. These quasiparticles are reminiscent of two-electron excitations of the negatively charged hydrogen ion and are subject to autoionization - a unique scattering pathway available for excited states. I will further illustrate the impact of free carriers on the exciton transport revealing non-monotonous density dependence and highly efficient propagation of charged exciton complexes. Finally, I will demonstrate electrically tunable trions in hybrid organic-inorganic semiconductors. These three-particle complexes feature unusually large binding energies combined with substantial mobility at elevated temperatures.
    Close abstract

    Ph.D thesis: Pushing the envelope of high field DNP-NMR methodology towards functional materials

    Date:
    20
    Wednesday
    July
    2022
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Asya Svirinovsky
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Functional materials are the main building blocks of advanced technologies based ... Read more Functional materials are the main building blocks of advanced technologies based on energy storage and conversion systems essential for our modern life including batteries, solar cells, and heterogeneous catalysis. Improvements in materials performance and development of new materials rely on our ability to obtain structure-function correlation as well as understand degradation processes when the materials are integrated into a device. To this end, advanced analytical tools that can provide information at the atomic level are essential. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy is well suited for this task, especially when equipped with high sensitivity by Magic Angle Spinning - Dynamic Nuclear Polarization (MAS-DNP). However, to date, the majority of materials studied by MAS-DNP were non-reactive and non-conductive materials with DNP from exogenous sources of polarization such as nitroxide radicals. This approach cannot be simply extended to functional materials as the properties that stem from the material’s functionality in the device, including electrical conductivity, chemical reactivity and defects, often pose challenges in the study of the materials by DNP. In this talk I will frame the challenges associated with the application of MAS-DNP to functional materials and describe approaches to address them. Results will be presented from three ubiquitous material systems spanning a range of applications: carbon allotropes, transition metal dichalcogenides (TMDs) and metallic microstructures. We systematically investigated the deleterious effect of materials’ conductivity and formulated means to reduce the effect. We explored the feasibility of utilizing inherent unpaired electrons for endogenous DNP and applied it to probe buried phases in all-solid-state lithium-metal battery and the surface chemistry in carbons. I will show that wealth of information achieved by DNP on various functional materials, can place DNP-NMR as a preferable tool for materials scientists. Our findings are expected to apply to many other systems where functional materials are dominant, making DNP a more general technique.
    Close abstract

    WIS-Q Seminar

    Date:
    10
    Sunday
    July
    2022
    Lecture / Seminar
    Time: 13:00
    Title: Quantum Sensing
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Amit Finkler
    Organizer: Department of Condensed Matter Physics
    Contact: Inna.dombrovsky@weizmann.ac.il
    Abstract: The second quantum revolution relies on our ability to control and measure indiv ... Read more The second quantum revolution relies on our ability to control and measure individual quantum states in micro- and nanoscopic systems, such as atoms, ions, and quantum dots. The techniques resulting from this capability may lead to a considerable improvement in several sensing modalities, for example atomic clocks and the measurement of magnetic fields on the nanoscale. As an example for a quantum sensor, and of course after introducing the underlying concepts of quantum sensing, I will present the nitrogen-vacancy defect, or color center, in diamond. First, I will explain how one can use it to measure magnetic and electric fields, temperature, strain and even pH levels. Then, I will try to show what the "quantum advantage" that is possible in this class of sensors and will give a few examples from research activities in our group. Finally, I will also discuss several industrial applications, some of which are already in use or in development around the world.
    Close abstract

    “Aspects of solar cell operation and reliability in High and low dimensions”

    Date:
    06
    Wednesday
    July
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Jean Francois Guillemoles
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: The development of advanced photovoltaic devices, including those that might ove ... Read more The development of advanced photovoltaic devices, including those that might overcome the single junction efficiency limit, as well as the development of new materials, all rely on advanced characterization methods. Among all the existing methods optically based ones are very well adapted to quantitatively probe optoelectronic properties at any stage. We here present the use of multidimensional imaging techniques that record spatially, spectrally and time resolved luminescence images. We will discuss the benefits (and challenges) of looking into energy conversion systems from high dimensions perspective and those of dimensional reduction for improved intelligibility through some examples, mostly drawn from halide perovskite materials and device. These examples will help visit questions related to efficient transport and conversion in solar cells, as well as questions related to chemical and operational stability of the devices.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    30
    Thursday
    June
    2022
    Colloquium
    Time: 11:15-12:30
    Title: The construction of the Vera Rubin Observatory and cosmological measurements of dark matter and dark energy with LSST
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Zeljko Ivesic
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: The Legacy Survey of Space and Time (LSST), the first project to be undertaken ... Read more The Legacy Survey of Space and Time (LSST), the first project to be undertaken at the new Vera Rubin Observatory, will be the most comprehensive optical astronomical survey ever undertaken. Starting in 2024, Rubin Observatory will obtain panoramic images covering the sky visible from its location in Chile every clear night for ten years. The resulting hundreds of petabytes of imaging data, essentially a digital color movie of the night sky, will include about 40 billion stars and galaxies, and will be used for investigations ranging from cataloging dangerous near-Earth asteroids to fundamental physics such as characterization of dark matter and dark energy. I will start my presentation with an overview of LSST science drivers and system design, and continue with a construction status report for the Vera Rubin Observatory. I will conclude with a brief discussion of a few Big Data challenges that need to be addressed before LSST data can be used for precise cosmological measurements.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    23
    Thursday
    June
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Revealing the Universe through Gravitational-wave Observations
    Location: https://weizmann.zoom.us/j/94565742701?pwd=UlZvQUFsaUlEVHM4UGIyNEllc2xjUT09
    Lecturer: David Reitze
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: Recent detections of gravitational waves (‘ripples in spacetime’) have produ ... Read more Recent detections of gravitational waves (‘ripples in spacetime’) have produced startling revelations about the nature of the high energy Universe. Since the first direct detection of gravitational waves in 2015 emitted by the collision and merger of two black holes located more than one billion light years away, we are beginning to answer fundamental and long standing questions about black holes, neutron stars, gravity, and even the origins of the heaviest elements found in nature.
    Close abstract

    Coupled Colloidal Quantum Dot Molecules

    Date:
    20
    Monday
    June
    2022
    Colloquium
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Uri Banin
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: Colloidal semiconductor Quantum Dots (CQDs) containing hundreds to thousands of ... Read more Colloidal semiconductor Quantum Dots (CQDs) containing hundreds to thousands of atoms have reached an exquisite level of control, alongside gaining fundamental understanding of their size, composition and surface-controlled properties, leading to their technological applications in displays and in bioimaging. Inspired by molecular chemistry, deeming CQDs as artificial atom building blocks, how plentiful would be the selection of composition, properties and functionalities of the analogous artificial molecules? Herein we introduce the utilization of CQDs as basic elements in nanocrystal chemistry for construction of coupled colloidal nanocrystals molecules. Focusing on the simplest form of homodimer quantum dots (QDs), analogous to homonuclear diatomic molecules, we introduce a facile and powerful synthesis strategy with precise control over the composition and size of the barrier in between the artificial atoms to allow for tuning the electronic coupling characteristics and their optical properties. This sets the stage for nanocrystals chemistry to yield a diverse selection of coupled CQD molecules utilizing the rich collection of artificial atom core/shell CQD building blocks. Such CQD molecules are of relevance for numerous applications including in displays, photodetection, biological tagging, electric field sensing and quantum technologies.
    Close abstract

    Physics Hybrid colloquium

    Date:
    16
    Thursday
    June
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Statistical Mechanics of Mutilated Sheets and Shells
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: David R. Nelson
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: Understanding deformations of macroscopic thin plates and shells has a long and ... Read more Understanding deformations of macroscopic thin plates and shells has a long and rich history, culminating with the Foeppl-von Karman equations in 1904, a precursor of general relativity characterized by a dimensionless coupling constant (the "Foeppl-von Karman number") that can easily reach vK = 10^7 in an ordinary sheet of writing paper. However, thermal fluctuations in thin elastic membranes fundamentally alter the long wavelength physics, as exemplified by experiments that twist and bend individual atomically-thin free-standing graphene sheets (with vK = 10^13!) With thermalized graphene sheets, it may be possible to study the quantum mechanics of two dimensional Dirac massless fermions in a fluctuating curved background whose dynamics resembles a simplified form of general relativity. We then move on to analyze the physics of sheets mutilated with puckers and stitches. Puckers and stitches lead to Ising-like phase transitions that strongly affect the physics of the fluctuating sheet. Thin shells with a background curvature that couples in-plane stretching modes with the out-of-plane undulations, exhibit a critical size for thermalized spherical shells, beyond which they must inevitably collapse.
    Close abstract

    WIS-Q Seminar

    Date:
    12
    Sunday
    June
    2022
    Lecture / Seminar
    Time: 13:00
    Title: Topological Superconductivity, Majorana fermions, and their Application to Quantum Computation
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof Yuval Oreg
    Organizer: Department of Condensed Matter Physics
    Contact: Inna.dombrovsky@weizmann.ac.il
    Details: A topological superconductor is a unique state of matter. Its non-Abelian varian ... Read more A topological superconductor is a unique state of matter. Its non-Abelian variant has zero- energy excitations (or particles) known as the Majorana zero modes. These modes have emerged as a critical component for topological quantum computation. Similar to a classical ferromagnet state, in which the interactions between the spins suppress single spin fluctuations, the topological superconductor self-corrects errors in the qubit operations carried by the Majorana zero modes. This talk will briefly discuss the Majoranas' unique non- abelian character and how we can use them to achieve fault-tolerance quantum processing. We will describe how the Majorana zero modes emerge in topological superconductors, the current experimental progress in finding this unique state of matter in nature, and the strategies to address the challenges in its realization.
    Close details

    New solid-state NMR methods for exciting and separating anisotropic interactions of spin I = 1 nuclei

    Date:
    26
    Thursday
    May
    2022
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Rihard Aleksis
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Solid-state NMR has become an essential tool for structural characterisation of ... Read more Solid-state NMR has become an essential tool for structural characterisation of materials, in particular systems with poor crystallinity and structural disorder. In recent years, a surge of interest has been observed for the study of paramagnetic systems, in which the interaction between nuclei and unpaired electrons allows to probe the electronic structure and properties of materials more directly. However, simultaneously this interaction leads to very broad resonances, which are dicult to acquire and interpret. While signi cant advancements in both NMR instrumentation and methodology have paved the way for the study of spin I = 1=2 nuclei in these systems, still many issues remain to be resolved for routine investigation of quadrupolar nuclei I > 1=2. Here we focus on improving both the excitation of the broad resonances and the resolution in the spectra of spin I = 1 nuclei. The latter problem is addressed by developing methods for separation of the shift and the quadrupolar interactions. We introduce two new methods under static conditions, which have the advantage over previous experiments of both suppressing spectral artefacts and exhibiting a broader excitation bandwidth. Furthermore, we demonstrate for the rst time an approach for separation of the anisotropic parts of the shift and quadrupolar interaction under magic-angle spinning. Secondly, to achieve broadband excitation we develop a new theoretical formalism for phase-modulated pulse sequences in rotating solids, which are applicable to nuclear spins with anisotropic interactions substantially larger than the spinning frequency, under conditions where the radio-frequency amplitude is smaller than or comparable to the spinning frequency. We apply the framework to the excitation of double-quantum spectra of 14N and design new pulse schemes with -encoded properties. Finally, we employ the new sequences together with density functional theory calculations to elucidate the electron and hydride ion conduction mechanisms in barium titanium oxyhydride.
    Close abstract

    Israel Physics Colloquium

    Date:
    23
    Monday
    May
    2022
    Colloquium
    Time: 00:00
    Title: Quantum gas in a box
    Location: https://weizmann.zoom.us/j/94885314520?pwd=Q2pra0dyS284VENiUVVhWGVTTjJFQT09
    Lecturer: Prof.  Zoran Hadzibabic
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: Meeting ID: 948 8531 4520 Password: 192379
    Abstract: For nearly three decades, ultracold atomic gases have been used with great succe ... Read more For nearly three decades, ultracold atomic gases have been used with great success to study fundamental many-body phenomena such as Bose-Einstein condensation and superfluidity. While traditionally they were produced in harmonic electromagnetic traps and thus had inhomogeneous densities, it is now also possible to create homogeneous samples in the uniform potential of an optical box trap. Box trapping simplifies the interpretation of experimental results, provides more direct connections with theory and, in some cases, allows qualitatively new, hitherto impossible experiments. I will give an overview of our recent experiments with box-trapped three- and two-dimensional Bose gases, focusing on a series of related experiments on non-equilibrium phenomena, including phase-transition dynamics, turbulence, and equilibration of closed quantum systems
    Close abstract

    Chemical and Biological Physics Guest Seminar

    Date:
    19
    Thursday
    May
    2022
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Single-Molecule Measurements Probe Nanoscale Physics and Chemistry
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Latha Venkataraman
    Organizer: Department of Chemical and Biological Physics
    Contact: oren.tal@weizmann.ac.il
    Abstract: Over the past decade, there has been tremendous progress in the measurement, mod ... Read more Over the past decade, there has been tremendous progress in the measurement, modeling and understanding of structure-function relationships in single molecule circuits. Experimental techniques for reliable and reproducible single molecule junction measurements have led, in part, to this progress. In particular, the scanning tunneling microscope-based break-junction technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Although the break-junction technique is mostly used to measure electronic properties of single-molecule circuits, in this talk, I will demonstrate its versatile uses to understand both physical and chemical phenomena with single-molecule precision. I will discuss some recent experimental and analysis aimed at understanding quantum interference in single-molecule junctions. I will then show an example where molecular structure can be designed to utilize interference effects to create a highly non-linear device. Finally, I will discuss some new areas of research aiming to demonstrate that electric fields can catalyze chemical reactions.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    19
    Thursday
    May
    2022
    Colloquium
    Time: 11:15-12:30
    Title: X-ray polarimetry for detection of vacuum birefringence & The Helium hydride ion in strong laser fields
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Dr. Gerhard G. Paulus
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: X-ray precision polarimetry and the detection of vacuum birefringence Vacuum ... Read more X-ray precision polarimetry and the detection of vacuum birefringence Vacuum isn’t just empty space. Rather there is a continuous creation and annihilation of virtual pairs. A strong electric field can align them to a certain degree such that vacuum becomes birefringent – according to quantum electrodynamics. The effect has been predicted almost 90 years ago, but never been directly verified to date. We have been developing X-ray polarimetry over the past 12 years in order to detect vacuum birefringence. The current status is an extinction ratio of 11 orders of magnitude using channel-cut crystals. This is a figure not nearly matched by any other polarimeter in any spectral region. Besides the physics of X-ray polarimetry, I will also discuss the remaining issues for the detection of vacuum birefringence. The Helium hydride ion in strong laser fields The Helium hydride ion is considered to be the first molecule that has formed after the big bang, a fact already pointing to the fundamental importance of this ion. Nevertheless, its behavior in intense, ultrashort laser fields has not been addressed until recently. This is in strong contrast to another fundamentally important molecule, the hydrogen molecular ion, on which many thousands of papers have been published. I will discuss a series of experiments using different isotopologues of the Helium hydride ion at different wavelengths. The dissociation and ionization dynamics turns out to be vastly different from the hydrogen molecular ion. Moreover, it changes dramatically when moving from the near- to the mid-infrared spectral region. Although Helium hydride and the hydrogen molecule are isoelectronic, they can be seen as opposing extremes.
    Close abstract

    WIS-Q Seminar

    Date:
    12
    Thursday
    May
    2022
    Lecture / Seminar
    Time: 12:30-14:30
    Title: Photonic Route to Fault-tolerant Quantum Computing
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Barak Dayan
    Organizer: Department of Condensed Matter Physics
    Contact: inna.dombrovsky@weizmann.ac.il
    Abstract: I will describe the photonic approach to quantum computation, which is the only ... Read more I will describe the photonic approach to quantum computation, which is the only technology that has been originally designed to reach the massive scaling required for fault- tolerant universal computation (> 106 physical qubits). It combines topological error correction and measurement-based quantum computation, with the leading effort relying on massive-scale silicon photonics. I will then describe how cavity-QED with single atoms allows deterministic photon-atom two qubit gates, which in turn can drastically simplify the road towards fault-tolerant photonic quantum computing and improve its scaling to even larger numbers of physical qubits.
    Close abstract

    Physics colloquium

    Date:
    12
    Thursday
    May
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Measuring the universe with galaxy surveys
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Marko Simonovich
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...
    Abstract: The last decade has seen a tremendous improvement in theoretical understanding o ... Read more The last decade has seen a tremendous improvement in theoretical understanding of galaxy clustering on cosmological scales, which culminated in recent CMB-independent measurement of cosmological parameters from spectroscopic galaxy surveys. In particular, these results are in agreement with the CMB estimates of the Hubble constant and they provide an important additional piece of the Hubble tension puzzle. In this talk I will review the main theoretical and practical developments which led to this progress. I will also highlight the main lessons we learned so far and discuss further improvements that have to be made in order to optimally extract information from the ongoing galaxy surveys such as DESI and Euclid. I will conclude by arguing that in the next couple of years the large-scale structure will become as powerful probe of cosmology as the CMB, and show the immense potential that the combination of the two has in answering many of the open questions in cosmology, including resolution of the Hubble tension.
    Close abstract

    “Spin-orbit coupling and Kondo resonance in Co adatom on Cu(100) surface: DFT+ED study”

    Date:
    28
    Thursday
    April
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Alexander B. Shick
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: The studies of magnetic atoms adsorbed on non-magnetic surfaces provide a fundam ... Read more The studies of magnetic atoms adsorbed on non-magnetic surfaces provide a fundamental insights into the quantum many-body phenomena at the nanoscale. They imprint non-trivial signatures in STM measurements, and can serve as a prototype for potential applications in quantum information technology. Our work aims at the investigation of the electronic structure, spin and orbital magnetic character for the Co adatom on the top of Cu(100) surface. We make use of DFT combined with exact diagonalization of the multi-orbital Anderson impurity model, including the spin-orbit coupling. For the Co atom d-shell occupation nd=8, a singlet many-body ground state and Kondo resonance are found, when the spin-orbit coupling is included in the calculations. The differential conductance is evaluated in a good agreement with the STM measurements. This comparison is the most direct way to demonstrate the validity of our theoretical approximation. Our results illustrate the very essential role which the spin-orbit coupling is playing in a formation of Kondo singlet for the multi-orbital impurity in low dimensions.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    14
    Thursday
    April
    2022
    Colloquium
    Time: 11:15-12:30
    Title: A Modification of Quantum Mechanics
    Location: https://bit.ly/3vcxT4z
    Lecturer: Prof. David Kaplan
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, Tea and more...
    Abstract: We present a modification of quantum mechanics in which a specific class of stat ... Read more We present a modification of quantum mechanics in which a specific class of state-dependent term is added to the Schroedinger Equation. We show that this term produces non-trivial effects which amount to the ‘wave function talking to itself’. We show that these effects are nevertheless causal (don’t violate relativity) while having profound experimental consequences. We also show that this modification has a simple embedding in local quantum field theory. While the physical effects are dramatic, they are also fickle, in that their strength depends on the cosmological history of the wave function of the universe. We will present proposals for laboratory (e.g., AMO), astrophysical, and cosmological tests that could be done to discover such an effect.
    Close abstract

    Physics Hybrid Colloquium

    Date:
    12
    Tuesday
    April
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Topological Quantum Computation with Majorana zero-energy modes
    Location: https://weizmann.zoom.us/j/94565742701?pwd=UlZvQUFsaUlEVHM4UGIyNEllc2xjUT09
    Lecturer: Roman Lutchyn
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Details: 11:00 - Coffee, tea and more...(outside of the auditorium)
    Abstract: Abstract: Research in quantum computing has offered many new physical insights a ... Read more Abstract: Research in quantum computing has offered many new physical insights and a potential to exponentially increase the computational power that can be harnessed to solve important problems in science and technology. The largest fundamental barrier to building a scalable quantum computer is errors caused by decoherence. Topological quantum computing overcomes this barrier by exploiting topological materials which, by their nature, limit errors. In this colloquium, I will discuss how to engineer topological superconductors supporting Majorana zero-energy modes at the interface of a conventional superconductor and a semiconductor with spin-orbit interaction. I will present recent results by the Microsoft Quantum team consistent with the emergence of topological superconductivity in proximitized semiconductor nanowires. Finally, I will present a proposal for scalable quantum computing involving topological qubits which comprise of superconducting islands in a Coulomb blockade regime hosting aggregates of four or more Majorana zero modes.
    Close abstract

    Quantum Leap: How Quantum Computing is Advancing from Lab to Industry

    Date:
    11
    Monday
    April
    2022
    Conference
    Time: 16:30-20:00
    Location: David Lopatie Conference Centre
    Contact: sharon.fireman@weizmann.ac.il

    WIS-Q Seminar

    Date:
    10
    Sunday
    April
    2022
    Lecture / Seminar
    Time: 13:00
    Title: How Quantum Computing is Changing Cryptography
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Zvika Brakerski
    Organizer: Department of Condensed Matter Physics
    Contact: Inna.dombrovsky@weizmann.ac.il
    Details:
    Abstract: It is fairly well known that Shor's algorithm for Factoring and Discrete Logarit ... Read more It is fairly well known that Shor's algorithm for Factoring and Discrete Logarithm poses a challenge for cryptography in a quantum world. However, the implications of the viability of the quantum model on cryptography are much more profound, on a number of aspects. Naturally, it is harder to protect against quantum attackers than against classical ones, especially if the honest users remain classical. On the other hand, quantum computation and communication also present new tools that may assist in performing some cryptographic tasks. Further, the quantum model brings about new potential capabilities and cryptographic tasks that need to be explored, most basically the ability to prove that a potentially untrusted device indeed performs a quantum task. In the talk I will explain how computer scientists, and in particular cryptographers, perceive the quantum computing model. I will discuss some of the fundamental questions that come up when the quantum model is incorporated into cryptography, such as the security of "lattice assumptions" against quantum attacks, the rewinding problem in cryptographic reductions, and the notion of semi-quantum cryptography which addresses questions in classical-quantum interaction. No background in computer science or cryptography will be assumed. Hybrid seminar Location: Physics library (Benoziyo Physics building, second floor) Zoom link: https://weizmann.zoom.us/j/99771276053?pwd=K3N6NEpPemh6aDZ2dEpJUU5HRXo4UT09
    Close abstract

    M.Sc thesis defense: "Data-Driven Force Fields for Large Scale Molecular Dynamics Simulations of Halide Perovskites"

    Date:
    08
    Tuesday
    March
    2022
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Oz Yosef Mendelsohn
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Zoom Link: https://weizmann.zoom.us/j/99290579488?pwd=cUIyV05SMUQ0VDErNUtma1R ... Read more Zoom Link: https://weizmann.zoom.us/j/99290579488?pwd=cUIyV05SMUQ0VDErNUtma1RTL3BIQT09 In the last decade, halide perovskites (HaPs) have developed as promising new materials for a wide range of optoelectronic applications, notably solar energy conversion. Although their technology has advanced rapidly towards high solar energy conversion efficiency and advantageous optoelectronic properties, many of their properties are still largely unknown from a basic scientific standpoint. Due to the highly dynamical nature of HaPs, one of the main avenues for basic science research is the use of molecular dynamics (MD) simulations, which provide a full atomistic picture of those materials. One of the main limiting factors for such analysis is the time scale of the MD simulation. Because of the complexity of the HaP system, classical force field approaches do not yield satisfactory results and the most widely used force calculation approach is based on first-principles, namely on density functional theory (DFT). In recent years, a new type of force calculation approach has emerged, which is machine learned force fields (MLFF). These methods are based on machine learning (ML) algorithms. Their wide spread use is enabled by the ever-increasing computational power and by the availability of large-scale shared repositories of scientific data. Here, we have applied one MLFF algorithm, known as domain machine learning (GDML). After training a MLFF based on the GDML model, we observed that the MLFF fails in a dynamical setting while still showing low testing error. This has been found to be due to lack of full coverage of the simulation phase space. To address this issue, we have suggested the hybrid temperature ensemble (HTE) approach, where we create rare events that are training samples on the edge of the phase space. We achieve this by combing MD trajectories from a range of temperatures to a single dataset. The MLFF model, trained on the HTE dataset, showed increasing accuracy during the training process, while being dynamically stable for a long duration of MD simulation. The trained MLFF model also exhibited high accuracy for long-term simulations, showing remaining errors of the same magnitude of inherent errors in DFT calculation.
    Close abstract

    Magnetic-optical coupling in 2D semiconductors

    Date:
    21
    Monday
    February
    2022
    Colloquium
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Efrat Lifshitz
    Organizer: Faculty of Chemistry
    Contact: sarah.amzallag@weizmann.ac.il
    Abstract: The dual coupling between intrinsic magnetism and electronic properties garners ... Read more The dual coupling between intrinsic magnetism and electronic properties garners enormous attention nowadays, due to their influence on quantum technologies. The talk will elaborate on the mentioned topic in van der Waals transition metal tri-chalcogenides and two-dimensional (2D) perovskites, possessing one or more of the following magnetic properties: A long-range magnetic order (ferromagnetism, anti-ferromagnetism), an interfacial/structure driven Rashba spin-orbit, Overhauser magnetic polaron effects. The lamellar metal phosphor tri-chalcogenides (MPX3; M=metal, X=chalcogenide) possess a honeycomb arrangement of metal ions within a single layer, producing a ferromagnetic or anti-ferromagnetic arrangement, with a consequence influence on magneto-optical properties. The talk will display magneto-optical measurements, exposing routes for the long-range magnetism and the existence of valley degree of freedom in a few MPX3 (M= Mn, Fe). The results suggest that magnetism protects the spin helicity of each valley however, the coupling to anti-ferromagnetism lifts the valleys' energy degeneracy. 2D perovskite structures (e.g., (PEA)2PbI4) are composed of alternating organic-inorganic constituents. The talk will describe the most recent work, exposing the co-existence of a Rashba and the Overhauser effects, in a structure with an inversion of symmetry. The unexpected effect is explained theoretically by the breakage of symmetry through the exchange between structural configurations.
    Close abstract
    Magnetic-optical coupling in 2D semiconductors Colloquium website

    WIS-Q Seminar

    Date:
    13
    Sunday
    February
    2022
    Lecture / Seminar
    Time: 13:00
    Title: Trapped ions quantum computing – a tale of highly social qubits
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Roee Ozeri
    Organizer: Department of Condensed Matter Physics
    Contact: Inna.dombrovsky@weizmann.ac.il
    Details: Zoom link: https://weizmann.zoom.us/j/97075939412?pwd=WTIrMk1KSldxS3ZVejVzekNsY25XQT09
    Abstract: In this talk I will review the basic methods and the current state-of-the-art in ... Read more In this talk I will review the basic methods and the current state-of-the-art in trapped ion quantum computing and compare the advantages and disadvantages of this to other QC technologies. I will further describe the progress towards building the WeizQC - a trapped ion quantum computer at the Weizmann Institute of Science. In the second part of the talk I will describe one unique feature of trapped-ion qubits: their all-to-all connectivity. I will describe methods that use this connectivity to engineer multi-qubit gates and operations. Multi-qubit gates have many advantages, both for near term noisy quantum computers, as well as for achieving fault-tolerance. As an example I will show that using multi-qubit gates, the threshold for fault-tolerant quantum computing can be enlarged and the ratio of logical to physical qubit error reduced.
    Close abstract

    Zoom: "A Faster Path to Solar Fuels: New Approaches for Highly Efficient Materials for Photoelectrochemical Energy Conversion

    Date:
    06
    Sunday
    February
    2022
    Lecture / Seminar
    Time: 12:00-13:00
    Lecturer: Dr. Ronen Gottesman
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Zoom: https://weizmann.zoom.us/j/95703489711?pwd=Tyt5cU1tV2YrMFhYUytBU001bm4yQ ... Read more Zoom: https://weizmann.zoom.us/j/95703489711?pwd=Tyt5cU1tV2YrMFhYUytBU001bm4yQT09 Viable, global-scale photoelectrochemical energy conversion of cheap, abundant resources such as water into chemical fuels (“solar fuels”) depends on the progress of semiconducting light-absorbers with good carrier transport properties, suitable band edge positions, and stability in direct-semiconductor/electrolyte junctions. Investigations concentrated mainly on metal-oxides that offer good chemical stability yet suffer from poor charge transport than non-oxide semiconductors (e.g., Si, GaAs). Fortunately, only a fraction of the possible ternary and quaternary combinations (together ~ 105 – 106 combinations) were studied, making it likely that the best materials are still awaiting discovery. Unfortunately, designing controlled synthesis routes of single-phase oxides with low defects concentration will become more difficult as the number of elements increases; and 2) there are currently no robust and proven strategies for identifying promising multi-elemental systems. These challenges demand initial focusing on synthesis parameters of novel non-equilibrium synthesis approaches rather than chemical composition parameters by high-throughput combinatorial investigations of synthesis-parameter spaces. This would open new avenues for stabilizing metastable materials, discovering new chemical spaces, and obtaining light-absorbers with enhanced properties to study their physical working mechanisms in photoelectrochemical energy conversion. I will introduce an approach to exploring non-equilibrium synthesis-parameter spaces by forming gradients in synthesis-parameters without modifying composition-parameters, utilizing two non-equilibrium synthesis components: pulsed laser deposition and rapid radiative-heating. Their combination enables reproducible, high-throughput combinatorial synthesis, resulting in high-resolution observation and analysis. Even minor changes in synthesis can impact significantly material properties, physical working mechanisms, and performances, as demonstrated by studies of the relationship between synthesis conditions, crystal structures of α-SnWO4, and properties over a range of thicknesses of CuBi2O4, both emerging light-absorbers for photoelectrochemical water-splitting that were used as model multinary oxides.
    Close abstract

    Physics Virtual Colloquium

    Date:
    20
    Thursday
    January
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Experiments on superconducting processors at the dawn of NISQ era
    Location: https://weizmann.zoom.us/j/94565742701?pwd=UlZvQUFsaUlEVHM4UGIyNEllc2xjUT09
    Lecturer: Pedram Roushan
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Abstract: In 2019, the Google Quantum team demonstrated that certain computational tasks m ... Read more In 2019, the Google Quantum team demonstrated that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical computer, the quantum supremacy. Going beyond this milestone, we now seek to utilize these Noisy Intermediate Scale Quantum (NISQ) processors to find algorithms that are of interest to the broader scientific community. However, achieving this goal is an outstanding challenge both theoretically, e.g. in finding suitable algorithms, as well as experimentally, e.g. extending coherence of the system. By presenting some of our recent works, we discuss the challenges and our progress. In particular, we present results on preparing the ground state of the Toric code Hamiltonian using an efficient quantum circuit [1]. Combining various techniques, we study transitions to the time crystalline phase [2], which is challenging due to limited programmability, finite coherence time, and finite size of current processors. Our results demonstrate the promise of studying condensed matter problems with NISQ processors. [1] Satzinger et al., Science (2021) [2] Mi et al., Nature (2021)
    Close abstract

    Direct Imaging of Planet Formation

    Date:
    16
    Sunday
    January
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Sivan Ginzburg
    Organizer: Department of Earth and Planetary Sciences
    Contact: dalia.madhala@weizmann.ac.il
    Abstract: The vast majority of detected planets are observed indirectly, using their small ... Read more The vast majority of detected planets are observed indirectly, using their small perturbation on the light emitted by the host stars. In recent years, however, the world's largest ground based telescopes have succeeded in directly imaging the light coming from some planets themselves. I will present our comprehensive theory for the mass, luminosity, and spin of gas giant planets during their final stages of formation - when they simultaneously contract and accrete gas from a disk. I will apply this theory to the luminosity and spectrum obtained by the novel direct-imaging technique, highlighting the recently discovered PDS 70 system, where two planets were directly observed during formation for the first time.
    Close abstract

    WIS-Q Seminar

    Date:
    09
    Sunday
    January
    2022
    Lecture / Seminar
    Time: 13:00
    Title: Computing the Quantum: Classical and Quantum Simulations of Many-Body Systems
    Location: https://weizmann.zoom.us/j/95273631966?pwd=UjlhN2xIMnZERXNRcllGTnBxMWZPUT09
    Lecturer: Erez Berg
    Organizer: Department of Condensed Matter Physics
    Contact: Inna.dombrovsky@weizmann.ac.il
    Abstract: Many problems of interest, ranging from condensed matter physics and quantum che ... Read more Many problems of interest, ranging from condensed matter physics and quantum chemistry to quantum information, require finding the ground state of a system of many interacting degrees of freedom (e.g., qubits or quantum spins). The main challenge stems from the exponential scaling of the Hilbert space dimension with the number of qubits. I will first discuss various strategies to tackle this problem using classical computers, such as tensor network states and Monte Carlo sampling, and their limitations. Quantum computers are ideally suited for this task; I will present a proposal to simulate quantum systems on noisy intermediate-scale quantum (NISQ) devices made of imperfect qubits, where the noise level translates into a finite energy density (i.e., finite temperature).
    Close abstract

    Example 1 for internal event node

    Date:
    08
    Monday
    May
    2017
    -
    10
    Wednesday
    May
    2017
    Retreat
    Time: 10:00 - 12:30
    Location: David Lopatie Conference Centre ...
    Organizer: Department of ...
    Contact: weizmann@weizmann.ac.il

    Example 2 for internal event node

    Date:
    08
    Monday
    May
    2017
    -
    10
    Wednesday
    May
    2017
    Retreat
    Time: 10:00 - 12:30
    Location: David Lopatie Conference Centre ...
    Organizer: Department of ...
    Contact: weizmann@weizmann.ac.il