Bringing noble-gas spins into the light

In quantum science, we often encounter the tension between elongating the coherence time of a system and retaining the ability to control and interact with it. An extreme example is the nuclear spin of noble gases, which is isolated from the environment by the complete electronic shells. In our lab, the spins of a helium-3 gas maintain coherence for up to two hours. Unfortunately, these spins are not accessible to light in the optical domain, and their (potential) quantum qualities have been beyond reach and largely overlooked. We establish that thermal spin-exchange collisions between noble-gas atoms and alkali-metal atoms form a quantum interface between them. These weak collisions, despite their stochastic nature, accumulate to a deterministic, efficient, and controllable coupling between the collective spins of the two gases. In experiments, we realize the strong coupling between potassium and helium-3 spins and, by coupling light to the potassium spins, demonstrate an efficient, two-way, optical interface to the helium-3 spins. The interface paves the way to employing noble-gas spins in the quantum domain, and we discuss prospects for quantum memories and entanglement of distant noble-gas ensembles with hour-long lifetimes.

Geometric Frustration and the Intrinsic Approach in Soft Condensed Matter

Deducing the emergent behavior of a material from the properties of its molecular or atomic constituents is one of the greatest challenges of condensed matter theory. Considering many-body systems with highly cooperative ground states renders this task even more challenging. Geometrically frustrated assemblies are comprised of ill-fitting constituents that are associated with two or more tendencies that cannot be simultaneously reconciled, and thus lack a stress free rest state. The ground state of frustrated assemblies is highly cooperative, leading them to exhibit super-extensive energy growth, filamentation, size limitation and exotic response properties. Such systems arise in naturally occurring structures in biology and organic chemistry as well as in manmade synthetic materials. In this talk I will discuss how the intrinsic approach, in which matter is described only through local properties available to an observer within the material, overcomes the lack of a stress free rest state for frustrated assemblies and leads to a general framework. This framework in particular allows predicting the super-extensive energy exponent for sufficiently small systems. I will discuss its application to several specific systems exhibiting geometric frustration: growing elastic bodies, frustrated liquid crystals and twisted molecular crystals.

From Ultralight Dark Matter to Snowballs in Hell: a Tour in Particle Astrophysics

Astrophysical phenomena play a definitive role in our understanding of fundamental particle physics, and vice-verse. I will present two lines of research, showcasing the interplay between particle physics theory and astrophysics. In the first half of the talk, I will show how the viable parameter space for dark matter can be established using gravity alone. At the lowest end of the possible range for the dark matter particle mass, the de Broglie wavelength of ultralight dark matter (ULDM) attains astronomical scales. The ensuing wave mechanics phenomena can be tested observationally in a variety of astrophysical systems. I will describe a search for the imprint of ULDM on the gas kinematics of low-surface-brightness galaxies, leading to an absolute lower bound on the mass of dark matter. A host of other systems, ranging from supermassive black holes to gravitational lensing, offer promising means to advance the search for ULDM by orders of magnitude. In the second half of the talk, I will show how an analysis of cosmic ray antimatter — long considered a smoking gun for dark matter in the TeV range — has taken a surprising turn, leading us to new theoretical insights on the problem of the origin of loosely-bound nuclei in hadronic collisions (sometimes referred to as ``Snowballs in Hell”). The resulting research programme, now explored at the Large Hadron Collider, offers a bridge between two-particle correlation analyses to the study of nuclear clusters.

Visualizing Strongly-Interacting Quantum Matter

When quantum mechanics and Coulomb repulsion are combined in a pristine solid, some of the most fascinating electronic phases in nature can emerge. Interactions between electrons can form correlated insulators, electronic liquids, and in extreme cases even quantum electronic solids. These phases are predicted to exhibit their most striking features in real-space, however, they are also extremely fragile, preventing their visualization with existing experimental tools. In this talk, I will describe our experiments that use a pristine carbon nanotube as a new type of a scanning probe, capable of imaging electrical charge with unprecedented sensitivity and minimal invasiveness. I will show how using this platform we were able to obtain the first images of the quantum crystal of electrons, visualize the collective hydrodynamic flow of interacting electrons in graphene, and unravel the parent state that underlies the physics of strongly-interacting electrons in the recently-discovered system of magic angle twisted bilayer graphene.

Quantum Critical Metals

Metallic quantum critical phenomena are believed to play a key role in many strongly correlated materials, including high temperature superconductors. Theoretically, the problem of quantum criticality in the presence of a Fermi surface has proven to be highly challenging. However, it has recently been realized that many models used to describe such systems are amenable to numerically exact solution by quantum Monte Carlo (QMC) techniques, without suffering from the fermion sign problem. I will review the status of the understanding of metallic quantum criticality, and the recent progress made by QMC simulations. The results obtained so far will be described, as well as their implications for superconductivity, non-Fermi liquid behavior, and transport in the vicinity of metallic quantum critical points. Some of the outstanding puzzles and future directions are highlighted.

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Location: Edna and K.B. Weissman Building of Physical Sciences

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Location: Edna and K.B. Weissman Building of Physical Sciences

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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.

Testing 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.

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

Gravity, 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.

The 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.

Magic 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.

Attosecond 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.

ESO'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.

Special 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.

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.

Vortices 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.

The 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.

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

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.

The 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.

The 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.

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.

New 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.

Self-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.

Laboratory 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.

Physics Colloquium

Location: Edna and K.B. Weissman Building of Physical Sciences

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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.

Bose-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.

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.

Gene 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

Multiple 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

Electronic 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).

Tricks 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, oer 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.

Parity-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.