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June 18, 2020 |
Yuri Levin |
TBATBA
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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May 14, 2020 |
Rolf Kuiper |
TBATBA
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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April 23, 2020 |
Anthony Brown |
TBATBA
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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April 16, 2020 |
Jim Fuller |
TBATBA
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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March 5, 2020 |
Josh Simon |
Dwarf Galaxies as Astrophysical LaboratoriesDwarf Galaxies as Astrophysical Laboratories
Location: Edna and K.B. Weissman Building of Physical Sciences
The dwarf galaxies orbiting the Milky Way are the oldest, least luminous, most dark matter-dominated, and least chemically evolved stellar systems known. To begin, I will provide a brief introduction to these galaxies, highlighting the recent discovery of large numbers of ultra-faint dwarf galaxies. I will then explain how we can measure their dark matter content and describe some of the numerous ways that dwarfs are being used to constrain the properties of dark matter. Finally, I will show how chemical abundance measurements of dwarf galaxy stars provided critical insight into r-process nucleosynthesis prior to the LIGO discovery of a neutron star merger.
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February 20, 2020 |
Stefan Rotter |
Designing the optimal wave Designing the optimal wave
Location: Edna and K.B. Weissman Building of Physical Sciences
I will speak about newly emerging approaches for designing wave fronts that are optimal for various purposes such as for focusing waves on a target, for manipulating small particles with light, or for precision measurements in general. The theoretical concept enabling the optimal solutions for all of these diverse applications turns out to be an operator introduced by Wigner and Smith based on a system’s scattering matrix. I will provide a review of this concept and shall illustrate how experimental access to the Wigner-Smith operator enables wave-front shaping protocols at the optimal level of efficiency.
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February 13, 2020 |
Jordi Miralda-Escude |
Highly magnified gravitationally lensed stars as a probe to the nature of dark matterHighly magnified gravitationally lensed stars as a probe to the nature of dark matter
Location: Edna and K.B. Weissman Building of Physical Sciences
Dark matter continues to pose one of the most important questions in modern cosmology. Gravitationally lensed multiple images of galaxies, quasars and stars provide several opportunities for testing the clumpiness of dark matter on small scales due to, for example, compact objects, axion mini-clusters and waves, or subhalos orbiting on galactic or cluster dark matter halos. The idea of using highly magnified stars by lensing clusters to probe this small-scale granularity in the dark matter will be discussed.
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February 6, 2020 |
Guglielmo M. Tino |
Testing Gravity with Cold AtomsTesting Gravity with Cold Atoms
Location: Edna and K.B. Weissman Building of Physical Sciences
The ability to control the quantum degrees of freedom of atoms using laser light opened the way to precision measurements of fundamental physical quantities. I will describe experiments for precision tests of gravitational physics using new quantum devices based on ultracold atoms, namely, atom interferometers and optical clocks. I will report on the measurement of the gravitational constant G with a Rb Raman interferometer, on experiments based on Bloch oscillations of Sr atoms confined in an optical lattice for gravity measurements at small spatial scales, and on new tests of the Einstein equivalence principle. I will also discuss prospects to use atoms as new detectors for gravitational waves and for experiments in space. |
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January 30, 2020 |
Mordehai Milgrom |
Scale Invariance at low accelerations as an alternative to the dark UniverseScale Invariance at low accelerations as an alternative to the dark Universe
Location: Edna and K.B. Weissman Building of Physical Sciences
Galactic systems and the Universe at large exhibit significant anomalies when analyzed within Newtonian dynamics and general relativity: Large discrepancies are found between the gravitational masses required by the observed dynamics, and the masses we actually observe in these systems. The mainstream explanation of these anomalies invokes the dominant and ubiquitous presence of “dark matter”. The "MOND" paradigm suggests, instead, that the discrepancies are due to breakdown of standard dynamics in the limit of low accelerations, where MOND dynamics are space-time scale invariant. MOND accounts for many detailed manifestations of the mass discrepancies with no need for dark matter. I will outline the paradigm, some of its achievements, and some remaining problems and desiderata. |
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January 23, 2020 |
Eric Dufresne |
Growing Droplets in Cells and Gels Growing Droplets in Cells and Gels
Location: Edna and K.B. Weissman Building of Physical Sciences
To function effectively, living cells compartmentalize myriad chemical reactions. In the classic view, distinct functional volumes are separated by thin oily-barriers called membranes. Recently, the spontaneous sorting of cellular components into membraneless liquid-like domains has been appreciated as an alternate route to compartmentalization.
I will review the essential physical concepts thought to underly these biological phenomena, and outline some fundamental questions in soft matter physics that they inspire. Then, I will focus on the coupling of phase separation to elastic stresses in polymer networks. Using a series of experiments spanning living cells and synthetic materials, I will demonstrate that bulk mechanical stresses dramatically impact every stage in the life of a droplet, from nucleation and growth to ripening and dissolution.
These physical phenomena suggest new mechanisms that cells could exploit to regulate phase separation, and open new routes to the assembly of functional materials
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January 16, 2020 |
Yossi Nir |
The three jewels in the crown of the LHCThe three jewels in the crown of the LHC
Location: Edna and K.B. Weissman Building of Physical Sciences
The ATLAS and CMS experiments have made three major discoveries: The discovery of an elementary spin-zero particle, the discovery of the mechanism that makes the weak interactions short-range, and the discovery of the mechanism that gives the third generation fermions their masses. I explain how this progress in our understanding of the basic laws of Nature was achieved. |
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January 9, 2020 |
Matthew Headrick |
Gravity, entanglement, and bit threadsGravity, entanglement, and bit threads
Location: Edna and K.B. Weissman Building of Physical Sciences
In trying to understand quantum gravity at a fundamental level, one of the most confusing questions is where the degrees of freedom are. So-called holographic dualities help with this question, by showing that certain quantum gravity theories are equivalent to conventional quantum field theories, in which we understand in principle where the degrees of freedom are and how they interact. Using such dualities, a new way of understanding entanglement in quantum gravity, involving so-called “bit threads”, has recently been developed. From this point of view, space becomes a channel for carrying entanglement of fundamental degrees of freedom. We will explain what holographic dualities are, what bit threads are, and what they might tell us about the nature of space in quantum gravity. |
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January 2, 2020 |
Leonardo Rastelli |
Pulling Yourself by your Bootstraps in Quantum Field TheoryPulling Yourself by your Bootstraps in Quantum Field Theory
Location: Edna and K.B. Weissman Building of Physical Sciences
Quantum field theory (QFT) is the universal language of theoretical physics, underlying the Standard Model of elementary particles, the physics of the early Universe and a host of condensed matter phenomena such as phase transitions and superconductivity. A great achievement of 20th-century physics was the understanding of weakly coupled quantum field theories where interactions can be treated as small perturbations of otherwise freely moving particles. Critical challenges for the 21st century include solving the problem of strong coupling and mapping the whole space of consistent QFTs.
In this lecture, I will overview the bootstrap approach, the idea that theory space can be determined from the general principles of symmetry and quantum mechanics. This strategy provides a new unifying language for QFT and has allowed researchers to make predictions for physical observables even in strongly coupled theories. By holographic duality, the bootstrap program has also implications for the space of consistent quantum gravity theories. |
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December 26, 2019 |
Steven M. Kahn |
The Large Synoptic Survey Telescope: Status Update and Prospects for ScienceThe Large Synoptic Survey Telescope: Status Update and Prospects for Science
Location: Edna and K.B. Weissman Building of Physical Sciences
The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field ground-based telescope designed to provide a time-domain imaging survey of the entire southern hemisphere of sky in six optical colors (ugrizy). Over ten years, LSST will obtain ~ 1,000 exposures of every part of the southern sky, enabling a wide-variety of distinct scientific investigations, ranging from studies of small moving bodies in the solar system, to constraints on the structure and evolution of the Universe as a whole.
The development of LSST is a collaboration between the US National Science Foundation, which is supporting the development of the telescope and data system, and the US Department of Energy, which is supporting the development of the 3.2 gigapixel camera, the largest digital camera ever fabricated for astronomy. Approved in 2014, LSST is now well into construction, and is on track to beginning operations in 2022. I will review the design and technical status of the Project, and provide an overview of some of the exciting science highlights that we expect to come from this facility.
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December 19, 2019 |
Alex Ratzker |
Overcoming resolution limits with quantum sensing by utilising error correctionOvercoming resolution limits with quantum sensing by utilising error correction
Location: Edna and K.B. Weissman Building of Physical Sciences
Quantum sensing and metrology exploit quantum aspects of individual and complex systems to measure a physical quantity.
Quantum sensing targets a broad spectrum of physical quantities, of both static and time-dependent types.
While the most important characteristic for static quantities is sensitivity, for time-dependent signals it is the resolution, i.e. the ability to resolve two different frequencies.
The decay time of the probe imposes a fundamental limit on the quantum sensing efficiency. While error correction methods can prolong this time it was not clear if such a procedure could be used
in a quantum sensing protocol. In this talk I will present a study of spectral resolution problems with quantum sensors, and the development of a new super-resolution method that relies on quantum features for which the limitation imposed by the finite decay time can be partially overcome by error correction.
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December 12, 2019 |
Dmitri K. Efetov |
Magic Angle Bilayer Graphene - Superconductors, Orbital Magnets, Correlated States and beyondMagic Angle Bilayer Graphene - Superconductors, Orbital Magnets, Correlated States and beyond
Location: Edna and K.B. Weissman Building of Physical Sciences
When twisted close to a magic relative orientation angle near 1 degree, bilayer graphene has flat moire superlattice minibands that have emerged as a rich and highly tunable source of strong correlation physics, notably the appearance of superconductivity close to interaction-induced insulating states. Here we report on the fabrication of bilayer graphene devices with exceptionally uniform twist angles. We show that the reduction in twist angle disorder reveals insulating states at all integer occupancies of the four-fold spin/valley degenerate flat conduction and valence bands, i.e. at moire band filling factors nu = 0, +(-) 1, +(-) 2, +(-) 3, and reveals new superconductivity regions below critical temperatures as high as 3 K close to - 2 filling. In addition we find novel orbital magnetic states with non-zero Chern numbers. Our study shows that symmetry-broken states, interaction driven insulators, and superconducting domes are common across the entire moire flat bands, including near charge neutrality. We further will discuss recent experiments including screened interactions, fragile topology and the first applications of this amazing new materials platform. |
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December 5, 2019 |
Hans-Walter Rix |
What Processes Shape the Disks of Galaxies?What Processes Shape the Disks of Galaxies?
Location: Edna and K.B. Weissman Building of Physical Sciences
The Milky Way, as a very average spiral galaxy, can serve as a galaxy model organism to tell us which physical processes shape
the current structure and stellar content of galaxies: what sets the overall radial profile of the disk,
which the present-day orbital of any star, and how much formation memory does the Milky Way's disk retain?
We can now draw on global Galactic stellar surveys that constrain orbits, abundances and ages.
I will show how modelling these data now shows that global radial orbit migration is a very strong effect that
decisively shapes the structure of the Milky Way's disk. If the Milky Way is typical in this respect this
explains why galaxy disk profiles are exponential. And I will also sketch how data from the Gaia mission
can now tell us in far more detail the mechanisms that drive orbit evolution throughout our disk.
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November 28, 2019 |
Nirit Dudovich |
Attosecond InterferometryAttosecond Interferometry
Location: Edna and K.B. Weissman Building of Physical Sciences
Attosecond science is a young field of research that has rapidly evolved over the past decade. The progress in this field opened a door into a new area of research that allows one to observe multi-electron dynamics in atoms, molecules and solids. One of the most important aspect of attosecond spectroscopy lies in its coherent nature. Resolving the internal coherence is a primary challenge in this field, serving as a key step in our ability to reconstruct the internal dynamics. As in many other branches in physics, coherence is resolved via interferometry. In this talk, I will describe advanced schemes for attosecond interferometry. The application of these schemes provides direct insights into a range of fundamental phenomena in nature, from tunneling and photoionization in atomic systems to ultrafast chiral phenomena in molecules. |
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November 21, 2019 |
Vladimir Rosenhaus |
Quantum Many-Body Integrability, Solvability, and ChaosQuantum Many-Body Integrability, Solvability, and Chaos
Location: Edna and K.B. Weissman Building of Physical Sciences
This talk is concerned with the question: How can we characterize, find, and solve quantum field theories and many-body systems that exhibit features of quantum chaos? We describe the recently discovered Sachdev-Ye-Kitaev model: a quantum mechanical system of a large number of fermions with all-to-all quartic, Gaussian-random, interactions that, remarkably, is chaotic, nearly conformally invariant, and solvable. We contrast this with integrable two-dimensional quantum field theories, such as the Sine-Gordon model. We end with some comments on hopes for a framework to find nearly integrable quantum field theories that are nearly solvable. |
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November 14, 2019 |
Jason Spyromilio |
ESO's Extremely Large TelescopeESO's Extremely Large Telescope
Location: Edna and K.B. Weissman Building of Physical Sciences
The 39-m ELT is under construction by the European Southern Observatory. When completed
it will be the largest optical/NIR telescope in the world at one of the best sites. The talk shall
focus on the challenges associated with building this telescope and will describe the first generation
instrumentation complement and science drivers.
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November 7, 2019 |
Boaz Katz |
A new attempt to solve the type Ia supernova problemA new attempt to solve the type Ia supernova problem
Location: Edna and K.B. Weissman Building of Physical Sciences
Supernovae distribute most of the chemical elements that we are made of and are detected daily, yet we still do not know how they explode. Type Ia supernovae consist of most recorded supernovae and are likely the result of thermonuclear explosions of white dwarfs (common compact stars with mass similar to the sun and radius similar to earth), but what mechanism causes about 1% of white dwarfs to ignite remains unknown. I will describe our ongoing recent attempt to solve this puzzle that involves a new potential answer - direct collisions of white dwarfs in multiple stellar systems, new robust tools to compare explosion models to observations - in particular the use of global conservation of energy in emitted radiation, and new key observations - in particular late-time spectra of ~100 recent supernovae. |
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July 18, 2019 |
Dr. Osip Schwartz |
Special Physics ColloquiumSpecial Physics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
Laser manipulation of quantum particles, such as atoms, ions, and molecules, underpins much of modern physics. Electrons, too, can be coherently controlled by light. In this work, we study electron-laser interaction in free space and find that the conventional description based on the effective (ponderomotive) potential requires significant modification. We demonstrate laser-based phase manipulation of the electron wave function by performing interferometric experiments in a transmission electron microscope (TEM) and capture TEM images of the light wave. We then utilize the laser-induced phase shift to realize a nearly ideal phase plate for Zernike phase contrast TEM, solving a long-standing problem and addressing the challenge of dose-efficient interrogation of radiation-sensitive specimens. The laser phase plate is widely expected to advance the TEM studies of protein structure and cell organization. |
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July 4, 2019 |
Haim Beidenkopf |
Physics Colloquium Physics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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June 20, 2019 |
Ranny Budnik |
Physics Colloquium Physics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
The hunt for Dark Matter is reaching at a crossroads - after two decades of incredible pace, where five orders of magnitude in parameter space were covered, no unambiguous signal has emerged for interaction between the alleged particles and our normal, baryonic matter. The next generation detectors, aiming at another order of magnitude sensitivity increase, are on the runway, and the question of what will be next takes interesting turns.
I will cover the evidence for the existence of Dark Matter, present the state of the art results from the XENON1T experiment, and play with some novel ideas for the next step, trying to move the lamppost to where Dark Matter may still stay hidden.
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June 6, 2019 |
Prof. Yuval Grossman |
Neutrinos as the key to the universe as we know itNeutrinos as the key to the universe as we know it
Location: Edna and K.B. Weissman Building of Physical Sciences
There are three open questions in physics which seem unrelated: Why is there only matter around us? How neutrinos acquire their tiny masses? Why all particles in Nature have integer electric charges? It turns out that these open questions are related. In the talk I will explain these open questions, the connection between them, and describe the on-going theoretical and experimental efforts in understanding them.
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May 29, 2019 |
Prof. Nadya Mason |
Vortices in superconducting arrays: probing dissipation and interactionsVortices in superconducting arrays: probing dissipation and interactions
Location: Edna and K.B. Weissman Building of Physical Sciences
Superconductivity continues to be an exciting and fertile field of research, with potential applications in energy efficiency and storage. Non-superconducting systems in contact with superconductors have been of particular recent interest, as these proximity-coupled superconductors may show new behaviors or harbor unusual excitations (eg, Majoranas in topological-superconductor systems). A key to understanding and utilizing superconductors is understanding their behavior in magnetic fields, particularly when the field penetrates as quantized tubules of flux, or vortices. In this talk I will show that, although vortices have been studied for many years, measurements of their current-driven dynamics can still lead to new results and understanding. I will discuss transport measurements of current-driven vortices in superconductor-normal-superconductor (SNS) arrays, where we are able to access a number of vortex regimes, and find unusual behavior in the non-equilibrium transitions between vortex states. First, in the low magnetic field regime, we find that the dynamic behavior of vortices is consistent with the presence of time delayed dissipative forces. I will also discuss how at higher magnetic fields, vortex de-pinning occurs in two steps, consistent with a commensurate lattice appearing even for non-commensurate magnetic field values. This two-step behavior is due to strong vortex interactions, and has not previously been observed. Finally, I will discuss measurements of vortex arrays on topological insulators, where we see enhanced dissipation and evidence of unusual charged vortices, predicted as the “Witten effect” in topological systems.
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May 16, 2019 |
Prof. Amir Yacoby |
A New Spin On SuperconductivityA New Spin On Superconductivity
Location: Edna and K.B. Weissman Building of Physical Sciences
Mesoscopic physics, pioneered by Joe Imry nearly 4 decades ago, explores the behavior of matter on length scales where dimensionality, coherence, and interactions compete to produce material properties that are fundamentally different from their bulk counterparts. For example, the conventional wisdom of superconductivity, developed in 1957 by Bardeen, Cooper and Schrieffer (BCS) describes this state in terms of a condensate of electron pairs arranged in a spatially isotropic wave function with no net momentum or angular momentum (a spin-singlet configuration). However, on mesoscopic length scales entirely different types of superconductivity may be realized such as unconventional pairing where electrons are arranged in triplet rather than singlet configurations. Such superconductors
may enable dissipationless transport of spin and may also give rise to elementary excitations that do not obey the conventional Fermi or Bose statistics but rather have non-Abelian statistics where the exchange of two particles transforms the state of the system into a new quantum mechanical state.
In this talk I will describe some of our recent work that explores the proximity effect between a conventional superconductor and a semiconductor with strong spin-orbit interaction. Using supercurrent interference, we show that we can tune the induced superconductivity
continuously from conventional to unconventional, that is from singlet to triplet. Our results open up new possibilities for exploring unconventional superconductivity as well as provide an exciting new pathway for exploring non-Abelian excitation.
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April 18, 2019 |
Federica Petricca |
The dark Universe studied from deep underground: Exploring the low-mass frontierThe dark Universe studied from deep underground: Exploring the low-mass frontier
Location: Edna and K.B. Weissman Building of Physical Sciences
Today, many observations on various astronomical scales provide compelling evidence for the existence of dark matter. Its underlying nature, however, remains an open question of present-day physics.
The CRESST experiment is a direct dark matter search which aims to measure interactions of potential dark matter particles in an earth-bound detector, using scintillating CaWO4 crystals as target material operated as cryogenic calorimeters at millikelvin temperatures. Each interaction in CaWO4 produces a phonon signal in the target crystal and also a light signal that is measured by a secondary cryogenic calorimeter. This technology is particularly sensitive to small energy deposits induced by light dark matter particles, allowing the experiment to probe the low-mass region of the parameter space for spin-independent dark matter-nucleon scattering with high sensitivity.
Results obtained in the first run of CRESST-III with a detector achieving a nuclear recoil threshold of 30.1 eV, probing dark matter particle masses down to 0.16 GeV/c2, will be presented.
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April 4, 2019 |
Prof. Philip Walter |
Quantum photonics for a new level of computer security and enhanced quantum computer architecturesQuantum photonics for a new level of computer security and enhanced quantum computer architectures
Location: Edna and K.B. Weissman Building of Physical Sciences
The precise quantum control of single photons, together with the intrinsic advantage of being mobile make optical quantum system ideally suited for delegated quantum information tasks, reaching from well-established quantum cryptography to quantum clouds and quantum computer networks.
Here I present that the exploit of quantum photonics allows for a variety of quantum-enhanced data security for quantum and classical computers. The latter is based on feasible hybrid classical-quantum technology, which shows promising new applications of readily available quantum photonics technology for complex data processing. At the end I will also show how optical quantum computers allow for novel architectures that rely on superimposed order of quantum gates. As outlook I will discuss technological challenges for the scale up of photonic quantum computers, and our group’s current work for addressing some of those.
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March 28, 2019 |
Andrei bernevig |
Towards a Periodic Table Topological Materials Towards a Periodic Table Topological Materials
Location: Edna and K.B. Weissman Building of Physical Sciences
In the past few years the field of topological materials has uncovered many materials which have topological bands: bands which cannot be continuable to a trivial, “atomic” limit, and which are characterized by an integer topological index. We will review the progress in the field and the new types of topological behavior that is expected from the many predictions in the field. We will also show how, using a new theory called Topological Quantum Chemistry, thousands of new topological materials can be predicted, classified and discovered. The result is that- so far - out of 30000 materials investigated - at least 30 percent of all materials in nature can be classified as topological. One ultimately aims for a full classification of topological materials, available on database websites such as www.topologicalquantumchemistry.com
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March 14, 2019 |
Luis O. Silva |
Plasmas at the extremePlasmas at the extreme
Location: Edna and K.B. Weissman Building of Physical Sciences
Many astrophysical and laboratory scenarios share common underlying microphysics, and collective plasma effects associated with intense fields can have direct consequences on the plasma dynamics. These mechanisms, also involving QED effects, are highly nonlinear and multi scale, and require a combination of theory and large scale numerical simulations. The main challenges to address these scenarios will be discussed, as well as recent progresses triggered by large scale simulations of compact objects or of conditions in their vicinity, and developments on multi dimensional laser/beam plasma interactions in the presence of fields close to the critical Schwinger field, as expected in the most intense lasers now being built or in the most advanced particle accelerators. The connections between these scenarios will be discussed, emphasising the interplay between collective plasma dynamics and QED processes. Examples from both laboratory and astrophysical conditions will be provided.
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March 7, 2019 |
Jason Spyromilio |
The European Extremely Large Telescope The European Extremely Large Telescope
Location: Edna and K.B. Weissman Building of Physical Sciences
The European Southern Observatory is constructing a 39-m optical infrared telescope. This 1.2 Billion Euro project when completed in 2024 will be the largest telescope ever built with unprecedented collecting area and with Adaptive Optics incorporated diffraction limited operations are the baseline. The design and challenges of the project shall be described. Some aspects of the diverse science cases shall be presented as will the current technical status.
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February 28, 2019 |
Prof. Matias Zaldarriaga |
Challenges for physical cosmology after PlanckChallenges for physical cosmology after Planck
Location: Edna and K.B. Weissman Building of Physical Sciences
I will discuss the current status of physical cosmology after the latest Cosmic Microwave Background and other measurements. I will discuss the questions that still remain open in the field and how we might go about answering them. I will describe some recent theoretical developments that might contribute useful tools for overcoming some of the challenges that lie ahead.
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February 21, 2019 |
Prof. Shmuel Rubinstein |
The physics of crushing and smashingThe physics of crushing and smashing
Location: Edna and K.B. Weissman Building of Physical Sciences
Understanding the physics of irreversible processes that occur in far from equilibrium systems is of both fundamental and practical importance. However, these problems pose unique challenges as dynamic irreversible processes are far from steady and probing them requires keeping up with them as the system navigates across a complex landscape. Such challenges, as they manifest in turbulence, were beautifully portrayed by Richardson:
“Big whirls have little whirls that feed on their velocity, and little whirls have lesser whirls and so on to viscosity”
Lewis Fry Richardson (1922)
This statement captures the essence of the turbulent cascade—the conveyance of kinetic energy across scales that underlies the universal dynamics of turbulent flows. Indeed, such conveyance of important physical quantities (energy, stress, frustration and even information) down and up a vast range of scales underlie the dynamics of many systems. For example, these same concepts hold for multi-contact frictional interfaces that form and break, for correlated defect structures that determine the strength of metals, and even in intricate networks of creases that form when a thin sheet of paper is crumpled or a soda can is smashed. We have developed experimental techniques that enable one to capture these dynamic events across multiple time and length scales. In this talk, I will describe our observations on several irreversible systems using these new tools that shed new light on their far from equilibrium behavior.
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February 14, 2019 |
Christian Weinheimer |
Physics ColloquiumPhysics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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February 7, 2019 |
Prof. Ron Milo |
The Biomass Distribution on EarthThe Biomass Distribution on Earth
Location: Edna and K.B. Weissman Building of Physical Sciences
A census of the biomass on Earth is key for understanding the structure and dynamics of the biosphere. Yet, a quantitative, global view of how the biomass of different taxa compare with each other is still lacking. In this study, we harness recent advances in global sampling techniques to assemble the overall biomass composition of the biosphere, establishing the first census of the biomass of all the kingdoms of life.
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January 31, 2019 |
Charlie Markus |
Semiconductor-Superconductor Hybrids, Qubits, and Topology Semiconductor-Superconductor Hybrids, Qubits, and Topology
Location: Edna and K.B. Weissman Building of Physical Sciences
A few years ago, the first signs of a new emergent particle — Majorana modes — were obtained. It was an exciting development because Majoranas are predicted to show nonabelian particle-exchange statistics, which would be a first for any physical system. As if that weren’t enough, another motivation to develop this experimental observation into a controlled electronic device is that the use of topology in such systems is expected to yield unrivalled coherence in topological qubits made from Majoranas. The experimental situation is that we aren’t there yet, not because of unforeseen problems — in fact, the foreseen problems are hard enough. This talk will address where things stand, how’s the qubit, what are the challenges, and what is the future of this unconventional approach to quantum information.
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January 24, 2019 |
Prof. Benjamin Lev |
Playing with a quantum toy: Exploring thermalization near integrability with a magnetic quantum Newton's cradle Playing with a quantum toy: Exploring thermalization near integrability with a magnetic quantum Newton's cradle
Location: Edna and K.B. Weissman Building of Physical Sciences
Thermalization of near-integrable quantum systems is an unresolved question. We will present a new experiment that explores the emergence of thermalization in a quantum system by studying the dynamics of the momentum in a dipolar quantum Newton's cradle consisting of highly magnetic dysprosium atoms. This system constitutes the first dipolar strongly interacting 1D Bose gas. These interactions provide tunability of both the strength of the integrability-breaking perturbation and the nature of the near-integrable dynamics. The work sheds light on the mechanisms by which isolated quantum many-body systems thermalize and on the temporal structure of the onset of thermalization. We anticipate our novel 1D dipolar gas will yield insights into quantum thermalization and strongly interacting quantum gases with long-range interactions.
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January 17, 2019 |
Prof. Jenny Hoffman |
Imaging Topological MaterialsImaging Topological Materials
Location: Edna and K.B. Weissman Building of Physical Sciences
Today’s electronic technology – the pixels on the screen and the process to print the words on the page – are all made possible by the controlled motion of an electron’s charge. In the last decade, the discovery of topological band insulators with robust spin-polarized surface states has launched a new subfield of physics promising a new paradigm in computing. When topology is combined with strong electron correlations, even more interesting states of matter can arise, suggesting additional applications in quantum computing. Here we present the first direct proof of a strongly correlated topological insulator. Using scanning tunneling microscopy to probe the real and momentum space structure of SmB6, we quantify the opening of a Kondo insulating gap. Within that gap, we discover linearly dispersing surface states with the heaviest observed Dirac states in any material – hundreds of times the mass of a free electron. We show how single atom defects can scatter these surface states, which paves the way towards manipulating single atoms and thus controlling surface states and their excitations at the nanoscale.
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January 10, 2019 |
Frank C. van den Bosch |
New Insight into Cosmology and the Galaxy-Halo Connection from Non-Linear ScalesNew Insight into Cosmology and the Galaxy-Halo Connection from Non-Linear Scales
Location: Edna and K.B. Weissman Building of Physical Sciences
In our LCDM paradigm, galaxies form and reside in dark matter halos. Establishing the (statistical) relation between galaxies and dark matter halos, the `Galaxy-Halo connection', therefore gives important insight into galaxy formation, and also is a gateway to using the distribution of galaxies to constrain cosmological parameters. After a brief introduction to how clustering and gravitational lensing can be used to constrain the galaxy-halo connection, I show that several independent analyses all point towards a significant tension in cosmological parameters compared to the recent CMB results from the Planck satellite. I discuss the potential impact of assembly bias, and present satellite kinematics as a complementary and competitive method to constrain the galaxy-halo connection. After a brief historical overview of the use of satellite kinematics, I present two new analyses, and show how they can be used to improve our knowledge of the galaxy-halo connection.
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January 8, 2019 |
Dr. Sagi Ben-Ami |
G-CLEF and the search for Biomarkers in Exoplanets AtmospheresG-CLEF and the search for Biomarkers in Exoplanets Atmospheres
Location: Edna and K.B. Weissman Building of Physical Sciences
Following a review of G-CLEF – a first light High-R spectrograph for the Giant Magellan Telescope, I will present a concept extreme high resolution spectrograph optimized for molecular oxygen detection, a prominent biomarker in Earth atmosphere, using the transmission spectroscopy method. The instrument is based on the transmission properties of Fabry Perot Interferometers, and despite its modest dimensions is capable of achieving spectral resolution and sampling frequency in excess of R~300,000. I will discuss design parameters and the unique aspects that needs to be taken into account in the design of an FPI based instrument, and conclude with MC simulation results demonstrating the advantages of such a novel instrument.
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January 3, 2019 |
Prof. Bruno Eckhardt |
Self-similarity in boundary layersSelf-similarity in boundary layers
Location: Edna and K.B. Weissman Building of Physical Sciences
Boundary layers control the transport of momentum, heat, solutes and other quantities between walls and the bulk of a flow. The Prandtl-Blasius boundary layer was the first quantitative example of a flow profile near a wall and could be derived by an asymptotic expansion of the Navier-Stokes equation. For higher flow speeds we have scaling arguments and models, but no derivation from the Navier-Stokes equation.
The analysis of exact coherent structures in plane Couette flow reveals ingredients of such a more rigorous description of boundary layers. I will describe how exact coherent structures can be scaled to obtain self-similar structures on ever smaller scales as the Reynolds number increases.
A quasilinear approximation allows to combine the structures self-consistently to form boundary layers. Going beyond the quasilinear approximation will then open up new approaches for controlling and manipulating boundary layers.
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December 27, 2018 |
Prof. Nat Fisch |
Pushing particles with radio-frequency waves in plasma Pushing particles with radio-frequency waves in plasma
Location: Edna and K.B. Weissman Building of Physical Sciences
Pushing particles with rf waves can produce enormous effects in magnetically confined plasma. Through a variety of fundamental mechanisms, waves can drive as much as mega-amps of current parallel to a magnetic field. These currents produce fields that can confine the plasma in the steady state. Importantly, it was recently shown that currents driven precisely by these mechanisms can stabilize the tearing of the magnetic fields. Alternatively, waves can also drive ions perpendicular to a magnetic field. In a tokamak reactor, the result could be to facilitate economical fusion by diverting mega-amps of power. Another effect could be to rotate the plasma. Apart from their interest in natural settings, rapidly rotating plasmas exhibit unusual effects that can be exploited in Hall thrusters, plasma mass filters, and both inertial and magnetic fusion confinement devices.
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December 20, 2018 |
Daniel Savin |
Laboratory Astrophysics Studies along the Cosmic Cycle of GasLaboratory Astrophysics Studies along the Cosmic Cycle of Gas
Location: Edna and K.B. Weissman Building of Physical Sciences
Tracing the evolution of baryonic matter from atoms in space to stars such as our Sun hinges on an accurate understanding of the underlying physics controlling the properties of the gas at every step along this pathway. Here I will explain some of the key epochs in this cosmic cycle of gas and highlight our laboratory studies into the underlying atomic, molecular, plasma, and surface processes which control the observed properties of the gas.
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December 13, 2018 |
Ariel Amir |
From single-cell variability and correlations across lineages to the population growthFrom single-cell variability and correlations across lineages to the population growth
Location: Edna and K.B. Weissman Building of Physical Sciences
Genetically identical microbial cells often display diverse phenotypes. Stochasticity at the single-cell level contributes significantly to this phenotypic variability, and cells utilize a variety of mechanisms to regulate noise. In turn, these control mechanisms lead to correlations in various cellular traits across the lineage tree. I will present recent models we developed for understanding cellular homeostasis, with special focus on protein levels and cell size. These models allow us to characterize single-cell variability, including the emerging correlations and distributions. I will discuss the implications of stochasticity on the population growth. In contrast to the dogma, we find that variability may be detrimental to the population growth, suggesting that evolution would tend to suppress it.
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December 6, 2018 |
Roee Ozeri |
Physics ColloquiumPhysics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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November 29, 2018 |
Binghai Yan |
Discovery of Topological Materials in a Fusion of Physics and ChemistryDiscovery of Topological Materials in a Fusion of Physics and Chemistry
Location: Edna and K.B. Weissman Building of Physical Sciences
Over the past decade, the field of topological states has boosted frontline research in condensed matter physics. It is witnessed that the prediction and discovery of topological materials have stimulated the rapid development of this field. In this talk, I will overview the general concepts of topological states. In combination with computational methods, chemistry insights are found to be rather helpful to discover topological materials, to realize the beautiful concepts and phenomena in physics. For example, the topological Weyl fermions were recently discovered in realistic materials with topological Fermi arcs on the surface and exotic transport phenomena in the bulk.
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November 22, 2018 |
Prof. Vladan Vuletic |
Manipulating atoms with light: laser cooling to Bose-Einstein condensation and 51 atomic qubits Manipulating atoms with light: laser cooling to Bose-Einstein condensation and 51 atomic qubits
Location: Edna and K.B. Weissman Building of Physical Sciences
Since the first demonstration of laser cooling and trapping three decades ago, our abilities to manipulate atomic ensembles and individual atoms with light have been substantially extended. Among those novel capabilities, I will discuss a new method how to directly optically cool an atomic gas to form a Bose-Einstein condensate, without any evaporation. I will also discuss the deterministic preparation of a large array of individual atoms with controlled optically induced long-range Ising type interactions for quantum simulation, and potentially, quantum computing.
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October 25, 2018 |
Martin Weitz |
Bose-Einstein condensation of photonsBose-Einstein condensation of photons
Location: Edna and K.B. Weissman Building of Physical Sciences
Bose-Einstein condensation has been observed in several physical systems, including cold atomic gases, exciton-polaritons, and magnons. Photons usually show no Bose-Einstein con-densation, since for Planck’s blackbody radiation the particle number is not conserved and the photons at low temperatures vanish in the system walls. I here describe experiments with a dye-filled optical microresonator experimentally observing Bose-Einstein condensation of pho-tons. Thermalization is achieved in a number conserving way by repeated absorption re-emission cycles on the dye molecules, and the cavity mirrors provide both an effective photon mass and a confining potential. More recently, we have investigated calorimetric properties of the trapped photon gas, and determined both the heat capacity and the entropy around the phase transition. In other work, we have realized lattice potentials for photons in the dye mi-crocavity. In my talk, I will begin with a general introduction and give an account of current work and future plans of the Bonn photon gas experiment. |
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October 11, 2018 |
Immanuel Bloch |
Controlling and Exploring Quantum Matter Using Ultracold Atoms in Optical LatticesControlling and Exploring Quantum Matter Using Ultracold Atoms in Optical Lattices
Location: Edna and K.B. Weissman Building of Physical Sciences
More than 30 years ago, Richard Feynman outlined the visionary concept of a quantum simu-lator for carrying out complex physics calculations.
Today, his dream has become a reality in laboratories around the world. In my talk I will focus on the remarkable opportunities offered by ultracold quantum gases trapped in optical lattic-es to address fundamental physics questions ranging from condensed matter physics over sta-tistical physics to high energy physics with table-top experiment.
For example, I will show how it has now become possible to image and control quantum mat-ter with single atom sensitivity and single site resolution, thereby allowing one to directly im-age individual quantum fluctuations of a many-body system or directly reveal hidden topolog-ical antiferromagnetic order in the fermionic Hubbard model.
Finally, I will discuss our recent experiments on novel many-body localised states of matter that challenge our understanding of the connection between statistical physics and quantum mechanics at a fundamental level.
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September 27, 2018 |
Gerhard Rempe |
Special Physics Colloquium- Special Physics Colloquium-
Location: Edna and K.B. Weissman Building of Physical Sciences
Quantum physics allows for applications not possible within classical physics. A prominent example is the quantum computer that, once realized, needs a quantum communication environment – a quantum internet. With this in mind, the talk will discuss a unique toolbox for distributed quantum computation and quantum communication by means of photonic qubits that propagate between atomic quantum memories localized in optical resonators as quantum interfaces. |
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July 12, 2018 |
Adam Rubin, Gadi Afek, Yehonathan Drori, Efrat Gerchkovitz |
Students Colloquium
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July 5, 2018 |
David R. Nelson |
Gene Surfing and Survival of the LuckiestGene Surfing and Survival of the Luckiest
Location: Edna and K.B. Weissman Building of Physical Sciences
Range expansions play a crucial role in our evolutionary history and also in human health. Descriptions of stochastic processes similar to Fokker-Planck equations are crucial for understanding the effects of mutations, number fluctuations and selective advantages. Mutations optimally positioned at the front of a growing population can increase their abundance by |
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June 28, 2018 |
Naftali Tishby |
The Information Theory of Deep Neural Networks: The statistical physics perspectiveThe Information Theory of Deep Neural Networks: The statistical physics perspective
Location: Edna and K.B. Weissman Building of Physical Sciences
The surprising success of learning with deep neural networks poses two fundamental challenges: understanding why these networks work so well and what this success tells us about the nature of intelligence and our biological brain. Our recent Information Theory of Deep Learning shows that large deep networks achieve the optimal tradeoff between training size and accuracy, and that this optimality is achieved through the noise in the learning process.
In this talk, I will focus on the statistical physics aspects of our theory and the interaction between the stochastic dynamics of the training algorithm (Stochastic Gradient Descent) and the phase structure of the Information Bottleneck problem. Specifically, I will describe the connections between the phase transition and the final location and representation of the hidden layers, and the role of these phase transitions in determining the weights of the network.
Based partly on joint works with Ravid Shwartz-Ziv, Noga Zaslavsky, and Shlomi Agmon.
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June 21, 2018 |
Ron Lifshitz |
Multiple Scale Structures:From Faraday Waves to Soft QuasicrystalsMultiple Scale Structures:From Faraday Waves to Soft Quasicrystals
Location: Edna and K.B. Weissman Building of Physical Sciences
For many years, quasicrystals were observed only as solid-state metallic alloys, yet current research is actively exploring their formation in a variety of soft materials, including systems of macromolecules, nanoparticles, and colloids. Much effort is being invested in understanding the thermodynamic properties of these soft-matter quasicrystals in order to predict and possibly control the structures that form, and hopefully to shed light on the broader, yet unresolved, general questions of quasicrystal formation and stability. I shall give an explanation for the stability of certain soft-matter quasicrystals---inspired by the physics of a different phenomenon known as Faraday waves---and provide a recipe for designing pair potentials that yield so-called |
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June 14, 2018 |
Hillel Aharoni |
Making Faces: Universal Inverse Design of Surfaces with Anisotropic Soft Materials Making Faces: Universal Inverse Design of Surfaces with Anisotropic Soft Materials
Location: Edna and K.B. Weissman Building of Physical Sciences
Elastic bodies can be programmed to take different shapes in different environments using stimulus-responsive anisotropic materials, where the route of shape changes is encoded in the local direction of material anisotropy at every point. In this talk I tackle the key theoretical question underlying many recent efforts to implement this approach — the inverse design problem — namely, given an arbitrary shape, constructing the anisotropy field that would induce it. I show analytical solutions to certain classes of this problem and a numerical algorithm to construct any surface geometry, and I resolve the problem of properly converting these 2D geometries into their destined 3D shapes. Finally, I team up with an experimental group in realizing this scheme by imprinting our numerical solutions into liquid crystalline elastomer sheets. We show success in experimentally producing flat rubber-like sheets that, upon heating, take an arbitrary preprogrammed desired shape, such as a face. |
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June 7, 2018 |
Oren Tal |
Electronic noise due to temperature difference across atomic scale conductors: beyond standard thermal and shot noisesElectronic noise due to temperature difference across atomic scale conductors: beyond standard thermal and shot noises
Location: Edna and K.B. Weissman Building of Physical Sciences
Since the discovery of electronic thermal and shot noises a century ago, these two forms of fundamental noise have had an enormous impact on science and technology. They are regarded as valuable probes for quantum and thermodynamic quantities, but also as an undesired noise in electronic devices. While electronic thermal (Johnson–Nyquist) noise is activated by temperature, electronic shot noise is generated by a voltage difference. Recently, we identified a fundamental electronic noise contribution that is generated by temperature difference across nanoscale conductors. This noise, which we term as delta-T noise, is measured in atomic and molecular junctions, and analyzed theoretically using the Landauer–Büttiker–Imry formalism. The delta-T noise can be used to detect temperature differences across nanoscale conductors without the need for fabricating sophisticated local probes. This noise is also relevant for modern electronics! , since temperature differences are often unintentionally generated across electronic components. Taking into account the overlooked contribution of the delta-T noise in these cases, can be important for designing high performance electronics at the nanoscale.
This work was done in collaboration with the research groups of Dvira Segal (Toronto U.) and Abraham Nitzan (Tel Aviv U. & Penn).
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May 31, 2018 |
Kamran Behnia |
The Wiedemann-Franz law and its discontentsThe Wiedemann-Franz law and its discontents
Location: Edna and K.B. Weissman Building of Physical Sciences
In the middle of nineteenth century, Wiedemann and Franz discovered a correlation between thermal and electrical conductivities of various metals. Since then, a law bearing their name has become one of the oldest laws of the solid-state physics. It survived the quantum revolution, which linked it to a ratio of fundamental constants. The equality between this Sommerfeld ratio and the Lorenz number (the ratio of thermal conductivity divided by temperature to electric conductivity) in the zero-temperature limit was enshrined as a canonical signature of a Fermi liquid.
The subject of this talk is the experimental research on the validity of (and the deviations from) the Wiedemann-Franz law in uncommon metals. After reviewing different unsuccessful assaults in the past three decades, we will focus on ongoing research and the information brought by verifying this correlation. Two distinct contexts will be discussed. The first is strong electron-electron scattering and possible hydrodynamic signatures in the transport of charge and entropy. The second subject is anomalous transverse transport arising from the Berry curvature of Bloch waves. In both cases, the zero-temperature validity is accompanied by a finite-temperature deviation, a controversial source of information on mobile electrons in solids.
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May 24, 2018 |
Guy Ron |
Tricks and Traps:Low Energy Searches for High Energy PhysicsTricks and Traps:Low Energy Searches for High Energy Physics
Location: Edna and K.B. Weissman Building of Physical Sciences
Trapped radioactive atoms and ions have become a standard tool of the trade
for precision studies of beyond SM physics. decay studies, in particular,
o er the possibility of detecting deviations from standard model predictions
of the weak interaction which signal new physics. These 'precision frontier'
searches are complementary to the high energy searches performed by the
LHC and other high energy/high luminosity facilities.
I will present a general overview of magneto-optical, optical traps, and elec-
trostatic traps, and their use for weak interaction studies. I will further
present the new Hebrew University/Weizmann Institute/NRCN trapping
program (TRAPLAB), recent experimental results, and future plans. |
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May 17, 2018 |
TBA |
Physics ColloquiumPhysics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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May 10, 2018 |
Demetrios Christodoulides |
Parity-Time and other Symmetries in Optics and PhotonicsParity-Time and other Symmetries in Optics and Photonics
Location: Edna and K.B. Weissman Building of Physical Sciences
The prospect of judiciously utilizing both optical gain and loss has been recently suggested as a means to control the flow of light. This proposition makes use of some newly developed concepts based on non-Hermiticity and parity-time (PT) symmetry-ideas first conceived within quantum field theories. By harnessing such notions, recent works indicate that novel synthetic structures and devices with counter-intuitive properties can be realized, potentially enabling new possibilities in the field of optics and integrated photonics. Non-Hermitian degeneracies, also known as exceptional points (EPs), have also emerged as a new paradigm for engineering the response of optical systems. In this talk, we provide an overview of recent developments in this newly emerging field. The use of other type symmetries in photonics will be also discussed. |
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May 9, 2018 |
Y. Yamamoto |
COHERENT ISING MACHINE - OPTICAL NEURAL NETWORK OPERATING AT THE QUANTUM LIMITCOHERENT ISING MACHINE - OPTICAL NEURAL NETWORK OPERATING AT THE QUANTUM LIMIT
Location: Edna and K.B. Weissman Building of Physical Sciences
In this talk, we will present the basic concept, operational principle and experimental perfor-mance of a novel computing machine based on the network of degenerate optical parametric oscillators. The developed machine has 2048 qubits with all-to-all connections and is now available as a cloud system via internet.
There are at least three quantum computing models proposed today: they are unitary quan-tum computation, adiabatic quantum computation and dissipative quantum computation. A gate model quantum computer implements the unitary quantum computation model and is expected to solve particular problems with hidden periodicity or specific structure [1,2], while a coherent Ising machine (CIM), implements the dissipative quantum computation model [3,4] and is expected to solve unstructured combinatorial optimization problems. We will dis-cuss the two types of CIMs, optical delay line coupling machine [5] and measurement feed-back coupling machine [6], as well as the performance comparison against modern digital computers and algorithms [7].
References
[1] D. Deutsch, Proc. of the Royal Society of London. Series A, Mathematical and Physical Sciences, 400, 97–117 (1985); D. Deutsch and R. Jozsa, Proc. Roy. Soc. (London) A 439, 553-558 (1992).
[2] P. W. Shor, Proc. of the 35th Annual Symposium on Foundations of Computer Science, IEEE Computer Socie-ty Press,124-134 (1994).
[3] W. H. Zurek, Rev. Mod. Phys. 75, 715-775 (2003).
[4] F. Verstraete, M. M. Wolf, and J. I. Cirac, Nature Phys. 5, 633-636 (2009).
[5] A. Marandi Z. Wang, K. Takata, R. L. Byer, and Y. Yamamoto, Nature Photonics 8, 937-942 (2014); T. Inagaki, K. Inaba, R. Hamerly, K. Inoue, Y. Yamamoto, and H. Takesue, Nature Photonics 10, 415-419 (2016).
[6] T. Inagaki, Y. Haribara, K. Igarashi, T. Sonobe, S. Tamate, T. Honjo, A. Marandi, P. L. McMahon, T. Umeki, K. Enbutsu, O. Tadanaga, H. Takenouchi, K. Aihara, K. Kawarabayashi, K. Inoue, S. Utsunomiya, and H. Takesue, Science 354, 603-606 (2016); P. L. McMahon, A. Marandi, Y. Haribara, R. Hamerly, C. Langrock, S. Tamate, T. Inagaki, H. Takesue, S. Utsunomiya, K. Aihara, R. L. Byer, M. M. Fejer, H. Mabuchi, and Y. Yamamoto, Science 354, 614-617 (2016).
[7] Y. Haribara, H. Ishikawa, S. Utsunomiya, K. Aihara, and Y. Yamamoto, Quantum Sci. Tech. 2, 044002 (2017).
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May 3, 2018 |
TBA |
Nausicaa’s beach Nausicaa’s beach
Location: Edna and K.B. Weissman Building of Physical Sciences
Twenty years separate the morning when Odysseus sails away from Itaca and the afternoon in which he reaches the island of the Phaeacians. Two decades is also a fairly typical period since the first back-of-the-envelope draft of a (neutrino physics) experiment and the moment in which such an experiment makes an impact, some times even a major discovery. In this talk I will tell the tale of the first decade of the Neutrino Experiment with a Xenon TPC (NEXT), and how it has sailed in the turbulent but beautiful seas of neutrino less double beta decay searches. I will also play oracle and predict the future of the NEXT in the context of the upcoming effort to uplift the current experimental apparatus to ton scale target masses. Ultimately, we hope that NEXT will end up, like Ulises, meeting NAUSICAA, a future Next AparatUS with Improved CApAbilities. |
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April 22, 2018 |
Bernard Derrida |
The many faces of the Fisher-KPP equationThe many faces of the Fisher-KPP equation
Location: Edna and K.B. Weissman Building of Physical Sciences
The Fisher KPP equation describes the growth of a stable region into
an unstable medium.
It was introduced in 1937 both by the biologist and statistician
Fisherand by the mathematicians Kolmogorov, Petrovsky, Piscounov to describe the propagation of a favorable gene in a population.
It is one of the classical examples of the problem of velocity selection. It also appears in many other contexts, ranging from the theory of disordered systems and spin glasses to reaction diffusion problems, branching Brownian motion and models of evolution with selection.
This talk will try to review the main classical results on this equation as well as some recent progress.
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April 12, 2018 |
Yair Mintzker |
Jew Süss: Between Truth and FictionJew Süss: Between Truth and Fiction
Location: Edna and K.B. Weissman Building of Physical Sciences
Joseph Süss Oppenheimer—"Jew Süss"—is one of the most iconic figures in the history of an-ti-Semitism. Originally from Heidelberg, in 1733 Oppenheimer became the "court Jew" of the duke of the small German state of Württemberg. When the duke died unexpectedly a few years later, the Württemberg authorities arrested Oppenheimer, put him on trial, and con-demned him to death for unspecified "misdeeds." On February 4, 1738, Oppenheimer was hanged in front of a large crowd just outside Stuttgart. It was one of the most sensational exe-cutions of the entire eighteenth century.
This lecture by Prof. Yair Mintzker (Princeton University) is based on his new book, “The Many Deaths of Jew Süss: The Notorious Trial and Execution of an Eighteen Century Court Jew” (Princeton UP, 2017). It will concentrate on the tension between the historical figure of “Jew Süss” as reflected in eighteenth-century sources on the one hand, and, on the other hand, the widespread and often cynical use of this figure in later works of fiction, chief among them the vicious Nazi propaganda movie "Jew Süss,” which was made in 1940 at the behest of Joseph Goebbels.
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March 29, 2018 |
TBA |
Physics ColloquiumPhysics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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March 22, 2018 |
Prof. Randy Kamien |
The Softest CrystalsThe Softest Crystals
Location: Edna and K.B. Weissman Building of Physical Sciences
Usually, crystals have three-dimensional periodicity. Smectic liquid crystals, however, have one-dimensional order, even in three-dimensional samples. These systems, as simple as they might seem, connect the physics of biomembranes, superconductivity, and even special relativity. I will provide an introduction for non-specialists and show how this diverse set of ideas comes together in these very, very soft systems.
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March 15, 2018 |
Yoichi Ando |
Topological Insulators and SuperconductorsTopological Insulators and Superconductors
Location: Edna and K.B. Weissman Building of Physical Sciences
Topological insulators and superconductors are new quantum states of matter that are characterized by nontrivial topological structures of the Hilbert space. Recently, they attract a lot of attention because of the appearance of exotic quasiparticles such as spin-momentum-locked Dirac fermions or Majorana fermions on their edge/surface, which hold promise for various novel applications. In particular, localized zero-energy Majorana mode is expected to obey non-Abelian statistics and enable topological quantum computing. In this talk, I will introduce the basics of those materials and present some of the key contributions we have made in this new frontier, such as the synthesis of bulk-insulating topological insulators, discovery of topological crystalline insulator, and the discovery of nematic topological superconductor. |
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March 8, 2018 |
Chris Jarzynski |
Scaling Down the Laws of ThermodynamicsScaling Down the Laws of Thermodynamics
Location: Edna and K.B. Weissman Building of Physical Sciences
Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems often exhibit “thermodynamic-like” behavior – biomolecular motors convert chemical fuel into mechanical work, and individual polymer molecules exhibit hysteresis and dissipation when stretched and contracted. To what extent can the laws of thermodynamics be “scaled down” to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will review recent progress toward answering these questions.
The second law of thermodynamics is traditionally stated in terms of inequalities. For microscopic systems these inequalities can be replaced by stronger equalities, known as fluctuation relations, which relate equilib-rium properties to far-from-equilibrium fluctuations. The discovery and experimental validation of these rela-tions has stimulated interest in the feedback control of small systems, the closely related Maxwell demon par-adox, and the interpretation of the thermodynamic arrow of time. These developments have led to new tools for the analysis of non-equilibrium experiments and simulations, and they have refined our understanding of irreversibility and the second law.
I will also discuss challenges and open questions, including how to extend fluctuation relations to quantum systems, and how to formulate the first law of thermodynamics properly, when the interaction energy be-tween the system and its thermal surroundings cannot be neglected.
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March 8, 2018 |
Chris Jarzynski |
Scaling Down the Laws of ThermodynamicsScaling Down the Laws of Thermodynamics
Location: Edna and K.B. Weissman Building of Physical Sciences
Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems often exhibit “thermodynamic-like” behavior – biomolecular motors convert chemical fuel into mechanical work, and individual polymer molecules exhibit hysteresis and dissipation when stretched and contracted. To what extent can the laws of thermodynamics be “scaled down” to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will review recent progress toward answering these questions.
The second law of thermodynamics is traditionally stated in terms of inequalities. For microscopic systems these inequalities can be replaced by stronger equalities, known as fluctuation relations, which relate equilib-rium properties to far-from-equilibrium fluctuations. The discovery and experimental validation of these rela-tions has stimulated interest in the feedback control of small systems, the closely related Maxwell demon par-adox, and the interpretation of the thermodynamic arrow of time. These developments have led to new tools for the analysis of non-equilibrium experiments and simulations, and they have refined our understanding of irreversibility and the second law.
I will also discuss challenges and open questions, including how to extend fluctuation relations to quantum systems, and how to formulate the first law of thermodynamics properly, when the interaction energy be-tween the system and its thermal surroundings cannot be neglected.
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March 1, 2018 |
TBA |
Physics ColloquiumPhysics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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February 22, 2018 |
Claudia Felser |
Topological Materials with liquid electronsTopological Materials with liquid electrons
Location: Edna and K.B. Weissman Building of Physical Sciences
Topology a mathematical concept became recently a hot topic in condensed matter physics and materials science. One important criteria for the identification of topological material is the band inversion and the crystal symmetry. In my talkI focus on new topological semimetals: Weyl semimetals. Binary phoshides are the ideal material class for a systematic study of Weyl physics. Weyl points, a new class of topological phases was also predicted in NbP, NbAs. TaP, MoP and WP2. In NbP micro-wires we have observed the chiral anomaly but NbP has served also as a model system for astrophysics: realizing the gravitational anomaly in NbP and the hydrodynamic flow of electrons in WP2. MoP and WP2 show exceptional properties such as high conductivity higher than copper, high mobilties and a high magneto-resistance effect. In magnetic materials, the Berry curvature measured via the classical anomalous Hall effect helps to identify interesting candidates for magnetic topological materials and devices. In this talk, we discuss ARPES evidence for a general theme of high temperature superconductivity - cooperative enhancement and positive feedback loop of different interactions exemplified by electron-electron and electron-phonon interactions. The accumulated evidence comes from an expanded version of angle-resolved photoemission spectroscopy and its match to in-situ material synthesis. In such experiments, the precision measurements of electron’s energy, momentum and time dynamics provide evidence for cooperative interactions as a pathway to increase the superconducting transition temperature. An outlook for ARPES development and application for other quantum materials will also be discussed.
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February 15, 2018 |
Michael Moshe |
Geometric charges in Elastic Solids Geometric charges in Elastic Solids
Location: Edna and K.B. Weissman Building of Physical Sciences
The mechanics of many natural systems is governed by localized sources of stresses. Examples include "plastic events" that occur in amorphous solids under external stress, defects formation in graphene, and force-dipoles applied by cells adhered to an elastic substrate. Recent developments in a geometric formulation of elasticity theory paved the way for a unifying mathematical description of such singular sources of stress, as “geometric charges". In this talk I will review basic results in this field, focusing on the geometry and mechanics of two-dimensional solid bodies. I will demonstrate the applicability of this approach in three different problems: mechanical metamaterials, mechanics of Kirigami, and wrinkle patterns in geometrically-incompatible elastic sheets. |
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February 8, 2018 |
ZX Shen |
Quantum Materials – Insights from Einstein’s Electrons Quantum Materials – Insights from Einstein’s Electrons
Location: Edna and K.B. Weissman Building of Physical Sciences
Quantum Material, as exemplified by unconventional superconductors and topological insulators, is a fascinating and rapidly developing field of modern physics. High-temperature superconductivity in cupper and iron based materials, with critical temperature well above what was anticipated by the BCS, remains a major unsolved physics problem today. The challenge of this problem is symbolized by a complex phase diagram consists of intertwined states with extreme properties in addition to unconventional superconductivity. None of them can be described by conventional theory, thus compounding the difficulty to understand high-temperature superconductivity itself as these states are different manifestations of the same underlying physical system, making an integrated understanding a necessity.
Angle-resolved photoemission spectroscopy (ARPES), derived from Einstein’s formulation of photoelectric effect, has emerged as a leading experimental tool to push the frontier of this important field of modern physics. Over the last three decades, the improved resolution and carefully matched experiments have been the keys to turn this technique into a sophisticated many-body physics tool. As a result, ARPES played a critical role in setting the intellectual agenda by testing new ideas and discovering surprises. ARPES has impacted both the field of unconventional superconductors and topological phases of matter.
In this talk, we discuss ARPES evidence for a general theme of high temperature superconductivity - cooperative enhancement and positive feedback loop of different interactions exemplified by electron-electron and electron-phonon interactions. The accumulated evidence comes from an expanded version of angle-resolved photoemission spectroscopy and its match to in-situ material synthesis. In such experiments, the precision measurements of electron’s energy, momentum and time dynamics provide evidence for cooperative interactions as a pathway to increase the superconducting transition temperature. An outlook for ARPES development and application for other quantum materials will also be discussed.
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February 1, 2018 |
Ranny Budnik, Oren Raz, Binghai Yan |
Physics Young PIS Colloquium Physics Young PIS Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
Ranny Budnik
"Exploring the dark side with bright, pure crystals“
Dark matter surrounds us and passes through us, yet it has not been discovered, after over a decade of intense efforts. However, many "windows" to dark matter parameter space remain closed, and opening them has become a leading target for the particle cosmology community. I will go quickly through the basics of dark matter, detection methods and recent results, and present an effort we are pursuing in our lab at the Weizmann Institute, to develop a new type of detector, able to detect low mass dark matter, using rare defects in pure crystals.
Oren Raz
"Anomalous thermal relaxation: from your kitchen to trapped ions“
Take a cold system, and couple it to a hot environment. Evidently, the system will heat up. Surprisingly, many aspects of this common process are poorly understood. Examples range from the anomalous heating rate in trapped ions, where the observed heating rate is commonly three orders of magnitude higher than naively expected, to a "thermal overshoot" where the system's temperature, during the relaxation process, becomes higher than the environment's temperature.
Binghai Yan
“The history and new understanding of surface states”
"A story about the electronic state on the surface, from the Shockley state to the topological state."
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January 25, 2018 |
Scott Aaronson |
Complexity-Theoretic Foundations of Quantum Supremacy Experiments Complexity-Theoretic Foundations of Quantum Supremacy Experiments
Location: Edna and K.B. Weissman Building of Physical Sciences
In the near future, there will likely be special-purpose quantum computers with 50 or so high-quality qubits and controllable nearest-neighbor couplings. In this talk, I'll discuss general theoretical foundations for how to use such devices to demonstrate "quantum supremacy": that is, a clear quantum speedup for *some* task, motivated by the goal of overturning the Extended Church-Turing Thesis (which says that all physical systems can be efficiently simulated by classical computers) as confidently as possible.
Based on joint work with Lijie Chen, https://arxiv.org/abs/1612.05903
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January 18, 2018 |
TBA |
Physics ColloquiumPhysics Colloquium
Location: Edna and K.B. Weissman Building of Physical Sciences
TBA |
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January 11, 2018 |
Satya Majumdar |
KPZ storyKPZ story
Location: Edna and K.B. Weissman Building of Physical Sciences
The celebrated KPZ equation (Kardar, Parisi, Zhang, 1986) is an important milestone in statistical physics, originally introduced to describe the late time dynamics in two dimensional growth models. Over the last 30 years, the KPZ story has evolved in various interesting directions, making links on the way to different areas of physics and mathematics. This includes in particular the link to the famous Tracy-Widom distribution in random matrix theory. The story of KPZ is a very successful one, involving theoretical physics, mathematics and experiments--a fertile playground for interdisciplinary science. In this talk, I will review the evolution of the KPZ story, pointing out the important landmarks as I go along. At the very end, I will discuss some recent developments establishing a nice link between the KPZ height fluctuations and the edge physics in cold atom systems. |
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January 4, 2018 |
Julien Tailleur |
Statistical physics of active particlesStatistical physics of active particles
Location: Edna and K.B. Weissman Building of Physical Sciences
Active matter describes a large class of systems in which individual units are able to dissipate energy stored in the environment to generate self-propelling forces. These systems, driven out of thermal equilibrium at the microscopic scale, can be found in Nature or synthesized in the lab. From bacteria and molecular motors to bird flocks and fisch schools, through self-phoretic janus colloids or Quincke rollers, they display a wide range of phenomenologies without counterparts in equilibrium systems. In this colloquium, I will review recent progresses in the field of active matter and show how non-equilibrium statistical mechanics accounts for the emerging properties of active materials. In particular, I will discuss the anomalous mechanical properties of active systems, showing that their mechanical pressures generically do not satisfy equations of state. I will also discuss their collective behaviours, from the transition to collective motion to the so-called motility induced phase separation through which a liquid-gas phase coexistence can emerge in the absence of attractive forces. |
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December 28, 2017 |
Mario Livio |
Special Colloquium in honor of Prof. Shimon Levit’s 70th birthdaySpecial Colloquium in honor of Prof. Shimon Levit’s 70th birthday
Location: Edna and K.B. Weissman Building of Physical Sciences
HUMAN CURIOSITY
The ability to ask “why?” makes us uniquely human. Curiosity drives basic scientific research, is the engine behind creativity in all disciplines from the arts to technology, is a necessary ingredient in education, and a facilitating tool in every form of storytelling (literature, film, TV, or even a simple conversation) that delights rather than bores. In a fascinating and entertaining lecture, astrophysicist and bestselling author Mario Livio surveys and interprets cutting-edge research in psychology and neuroscience that aims at exploring and understanding the origin and mechanisms of human curiosity. As part of his research into the subject, Livio examined in detail the personalities of two individuals who arguably represent the most curious minds to have ever existed: Leonardo da Vinci and Richard Feynman. He also interviewed 9 exceptionally curious people living today, among them Fabiola Gianotti, the Director General of CERN (who is also an accomplished pianist), paleontologist Jack Horner, and the virtuoso lead guitarist of the rock band Queen, Brian May (who also holds a PhD in astrophysics), and Livio presents fascinating conclusions from these conversations. |
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December 21, 2017 |
TBA |
Quantization of heat flow in the fractional quantum Hall regimeQuantization of heat flow in the fractional quantum Hall regime
Location: Edna and K.B. Weissman Building of Physical Sciences
Quantum mechanics sets an upper bound on the amount of charge flow as well as on the amount of heat flow in ballistic one-dimensional channels. The two relevant upper bounds, which combine only fundamental constants, are the quantum of the electrical conductance, Ge=e2/h, and the quantum of the thermal conductance, Gth=0T=(π2kB2/3h)T. Remarkably, the latter does not depend on the particles charge, particles exchange statistics, and is expected also to be insensitive to the interaction strength among the particles. However, unlike the relative ease in observing the quantization of the electrical conductance, measuring accurately the thermal conductance is more challenging.
The universality of the Gth quantization in 1D ballistic channels was demonstrated for weakly interacting particles: phonons [1], photons [2], and in an electronic Fermi-liquid [3]. I will describe our recent experiments with heat flow in a strongly interacting system of 2D electrons in the fractional quantum Hall regime. In the lowest Landau level we studied particle-like states (v<½) and the more complex hole-like states (½<v<1), which carry counter propagating neutral (zero net charge) modes [4]. We found quantization of Gth=0T in all these abelian states. In the first-excited Landau level (2<v<3), we concentrated on the even-denominator v=5/2 state, and found fractional quantization of the thermal conductance, Gth=½0T – a definite mark of a non-abelian state - harboring Majorana excitations [5].
1. K. Schwab, et al., Nature 404, 974 (2000)
2. M. Meschke, et al., Nature 444, 187 (2006)
3. S. Jezouin, et al., Science 342, 601 (2013)
4. M. Banerjee et. al., Nature 545, 75 (2017)
5. M. Banerjee et. al., arXiv: 1710.00492
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December 14, 2017 |
Prof. Diedrik Wiersma |
Phototonics walking up a human hairPhototonics walking up a human hair
Location: Edna and K.B. Weissman Building of Physical Sciences
Nature provides an excellent source of inspiration for optical and mechanical materials.
In this talk, I will discuss opto-mechanical structures with nano scale precision.
In particular, I will show our recent results on micro/nano robotic elements that use light as source of energy and that are controlled by light as well.
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December 7, 2017 |
Prof. Grisha Falkovich |
Wonders of viscous electronicsWonders of viscous electronics
Location: Edna and K.B. Weissman Building of Physical Sciences
Quantum-critical strongly correlated systems feature universal collision-dominated collective transport. Viscous electronics is an emerging field dealing with systems in which strongly interacting electrons flow like a fluid. Such flows have some remarkable properties never seen before. I shall describe recent theoretical and experimental works devoted, in particular, to a striking macroscopic DC transport behavior: viscous friction can drive electric current against an applied field, resulting in a negative resistance, recently measured experimentally in graphene. I shall also describe conductance exceeding the fundamental quantum-ballistic limit, field-theoretical anomalies and other wonders of viscous electronics. Strongly interacting electron-hole plasma in high-mobility graphene affords a unique link between quantum-critical electron transport and the wealth of fluid mechanics phenomena.
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December 3, 2017 |
Eli Waxman, Avishay Gal Yam, Eran Ofek, Doron Kushnir |
Neutron star mergers: gravitational waves and nucleosynthesis of heavy elementsNeutron star mergers: gravitational waves and nucleosynthesis of heavy elements
Location: Edna and K.B. Weissman Building of Physical Sciences
: In this special event, motivated by the 2017 Physics Nobel prize and the recent first
detection of a neutron star merger via both gravitational waves and electromagnetic radiation,
we will review the recent discovery and its implications.
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November 30, 2017 |
Andrea Morello |
Scaling up single-atom spin qubits in siliconScaling up single-atom spin qubits in silicon
Location: Edna and K.B. Weissman Building of Physical Sciences
The modern information era is built on silicon nanoelectronic devices. The future quantum information era might be built on silicon too, if we succeed in controlling the interactions between individual spins hosted in silicon nanostructures.
Spins in silicon constitute excellent solid-state qubits, because of the weak spin-orbit coupling and the possibility to remove nuclear spins from the environment through 28Si isotopic enrichment. Substitutional 31P atoms in silicon behave approximately like hydrogen in vacuum, providing two spin 1/2 qubits -- the donor-bound electron and the 31P nucleus -- that can be coherently controlled [1,2], read out in single-shot [2,3], and are naturally coupled through the hyperfine interaction.
In isotopically-enriched 28Si, these single-atom qubits have demonstrated outstanding coherence times, up to 35 seconds for the nuclear spin [4], and 1-qubit gate fidelities well above 99.9% for both the electron and the nucleus [5]. The hyperfine coupling provides a built-in interaction to entangle the two qubits within one atom. The combined initialization, control and readout fidelities result in a violation of Bell’s inequality with S = 2.70, a record value for solid-state qubits [6].
Despite being identical atomic systems, 31P atoms can be addressed individually by locally modifying the hyperfine interaction through electrostatic gating [7]. Multi-qubit logic gates can be mediated either by the exchange interaction [8] or by electric dipole coupling [9].
Scaling up beyond a single atom presents formidable challenges, but provides a pathway to building quantum processors that are compatible with standard semiconductor fabrication, and retain a nanometric footprint, important for truly large-scale quantum computers.
[1] J.J. Pla et al., Nature 489, 541 (2012)
[2] J.J. Pla et al., Nature 496, 334 (2013)
[3] A. Morello et al., Nature 467, 687 (2010)
[4] J.T. Muhonen et al., Nature Nanotech. 9, 986 (2014)
[5] J.T. Muhonen et al., J. Phys.: Condens. Matt. 27, 154205 (2015)
[6] J.P. Dehollain et al., Nature Nanotech. 11, 242 (2016)
[7] A. Laucht et al., Science Advances 1, e1500022 (2015)
[8] R. Kalra et al., Phys. Rev. X 4, 021044 (2014)
[9] G. Tosi et al., Nature Communications 8:450 (2017)
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November 23, 2017 |
Lev Vaidman |
The past of a quantum particleThe past of a quantum particle
Location: Edna and K.B. Weissman Building of Physical Sciences
Textbooks of quantum mechanics lack the concept of the past of quantum systems. Few years ago I proposed to define the past of a quantum particle according the trace it leaves. While in many cases this definition provides a reasonable description, for a nested Mach-Zehnder interferometer it leads to a picture seemingly contradicting common sense: the particle leaves a trace in a place through which it could not pass. I will discuss recent theoretical and experimental studies of this controversial issue. |
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November 16, 2017 |
Prof. Gerald Gabrielse |
Small-Scale, Highly Precise Tests of the Standard Model and Its SymmetriesSmall-Scale, Highly Precise Tests of the Standard Model and Its Symmetries
Location: Edna and K.B. Weissman Building of Physical Sciences
The Standard Model of particle physics is the great success and the great frustration of modern physics. It is very surprising that the Standard Model can successfully predict what is measured to up to a part in 10^{12}, and yet be completely unable to explain either why a universe could survive the big bang or why it should be made of matter rather than antimatter. Low energy experiments play a crucial role in testing the Standard Model. The most precise prediction of the Standard Model, for example, was tested with one suspended electron used to make make the most accurate measurement of a property of an elementary particle. The symmetries of the Standard Model can be directly tested by comparing particles and antiparticles. Searches for physics beyond the Standard Model at energy scales at and above LHC energies are carried out by searching for an electric dipole moment of an electron in a polar molecule. |
