JQI Seminar

The fractional quantum Hall system is one of the most strongly correlated systems in the world, because its physics is fully dictated by the interaction between the electrons, with their kinetic energy having been fully suppressed by the magnetic field. Somewhat surprisingly, much of the vast phenomenology of the fractional quantum Hall effect is now understood not only qualitatively but with a microscopic precision that rivals, ideally, that of atomic physics. This has become possible thanks to the emergence of the topological particle called composite fermion.

Photonic graph (or cluster) states are of interest for applications in one-way quantum computing and in quantum networks. The lack of photon-photon interactions makes the generation of entangled photonic states challenging: it is either based on resource-intensive probabilistic processes using linear optics, or it requires nonlinear interactions through a matter system. Here we will consider the direct generation of photonic entangled graph states from controlled quantum emitters.

A dramatic consequence of the role of topology in the structure of quantum matter is the existence of topological invariants that are reflected in quantized response functions. In this talk we will discuss a new variant on this theme.  We introduce a non-linear frequency dependent D+1 terminal conductance that characterizes a D dimensional Fermi gas, generalizing the Landauer conductance in D = 1.

Quantum systems subject to both driving and dissipation often have complex, non-thermal steady states, and are at the forefront of research in many areas of physics, including quantum information processing.  For classical systems, microscopic time-reversal symmetry leads to open systems satisfying detailed balance; this symmetry makes it extremely easy to find their stationary states.  In this talk, I’ll discuss a new way to think about detailed balance in fully quantum settings based on the existence of a “hidden” time-reversal symmetry.  I’ll show how this symmetry connect

Abstract: The absolute and precise measurement of small forces and torques is a difficult task. I will give examples of small forces from several research topics, for example, measuring the gravitational constant, photon pressure forces, and new ways to calibrate torque screwdrivers. Several techniques, their strengths, but also their pitfalls will be illuminated. Thus, the audience will learn several valuable and fun metrological tools and gain an appreciation of the usefulness of these measurements to advance physics and society.

Abstract: Recent advances in investigating radiative association (RA) reactions by quantum dynamics methods have revealed troubling discrepancies when compared with the reaction rates obtained using statistical methods, sometimes differing by up to four orders of magnitude. Notoriously difficult to measure in the laboratory, RA experiments are necessary to test the application of theoretical models to real systems.

Ultracold dipolar molecules combine features of ultracold atoms and trapped ions. They promise new research avenues in quantum simulation, quantum computing, and quantum chemistry. But creating and taming ultracold systems of dipolar molecules is not a routine task. For example, Bose-Einstein condensates of dipolar molecules have not been created, yet.

Interactions between atoms and electromagnetic fields are at the core of nearly all quantum devices, with applications ranging from building quantum computers and networks, communicating quantum information over long distances, and developing quantum sensors of increasing precision. The miniaturization of these systems is critical to increasing their modularity as well as improving the efficacy of light-matter interactions by confining electromagnetic fields in small volumes.

In this seminar, I will discuss several recent and ongoing experimental efforts in the Purdy Lab (which specializes in quantum sensors and transducers with optical, mechanical, and microwave systems), with a focus on some often overlooked or least under-appreciated aspects of relatively simple measurements.  We have recently completed the first detailed study of acoustic blackbody radiation interacting with a nanomechanical system.  While the acoustic equivalent of the well-known electromagnetic blackbody radiation should be equally ubiquitous, there have been almost no experiment

Abstract: Quantum spin liquids are low temperature phases of magnetic materials in which quantum fluctuations prevent the establishment of long-range magnetic order. These phases support fractionalized spin excitations (spinons) coupled to emergent photons. In this talk, I will review the basic picture of how quantum electrodynamics emerges in 3D spin ice and then turn to several results regarding its `fine structure'.