Fall 2021

The quantum beats are a well-understood phenomenon that has long been used as a spectroscopic technique in various systems. Here we demonstrate two new aspects in understanding and using quantum beats - (i) coupling to the electromagnetic vacuum allows for beating without an initial superposition between the excited levels, and (ii) by detecting the transmission in the forward direction in a superradiant burst, quantum beats can be collectively enhanced, increasing the signal strength useful in systems with low signal-to-noise.

The development of atomic clocks with systematic uncertainties in the 10-18 range enables searches for the variation of fundamental constants, dark matter, and violations of Lorentz invariance. I will give an overview of dark matter searches and other fundamental physics studies with atomic and nuclear clocks and focus on development of clocks with the highest sensitivities to new physics. I will discuss recent advances in theory of novel clocks based on highly-charged ions and efforts to develop a nuclear clock.

The recent successful computation beyond the capability of classical computers has brought considerable attention to the Noisy Intermediate Scale Quantum (NISQ) processors. The only way to evaluate the promise of NISQ devices is to implement algorithms on them that are of interest to the scientific community.

The physics of cooperative atoms/radiators in regular 2D arrays is dominated by two properties: first, a strongly frequency-selective reflectivity and second, the ability to confine polariton modes cleanly on the surface. This makes such a system highly sensitive to and controllable by light fields. Applications of these systems include quantum information, metrology, and nonlinear single-photon techniques.

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.