Fall 2021

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.

We derive a family of optimal protocols, in the sense of saturating the quantum Cramér-Rao bound, for measuring a linear combination of d field amplitudes with quantum sensor networks, a key subprotocol of general quantum sensor networks applications. We demonstrate how to select different protocols from this family under various constraints via linear programming. Focusing on entanglement-based constraints, we prove the surprising result that highly entangled states are not necessary to achieve optimality for many problems.

We are pleased to announce the 2021 Janet Das Sarma Memorial CMTC Conference, a scientific conference in memory of Janet Das Sarma, who played a crucial behind-the scene role in making the Condensed Matter Theory Center at the University of Maryland (www.physics.umd.edu/cmtc/) a success and profoundly affected all aspects of the center.

Dissertation Committee Chair: Prof. Mohammad Hafezi, Co-Advisor
Committee: 
Dr. Glenn Solomon, Co-Advisor
Dr. Johnpierre Paglione
Dr. Jay Deep Sau
Dr. Thomas E. Murphy, Dean’s Representative
Abstract: