Fall 2022

Abstract: Arrays of neutral atoms promise to enable a variety of goals across quantum science, including quantum information processing, metrology, and many-body physics. While there have been recent significant improvements in quantum control, coherence times, and entanglement generation, one outstanding limitation is the efficient implementation of dissipation or measurement. An exciting possibility to overcome this challenge involves the integration of the atom array with an optical cavity, whereby strong coupling between atoms and light enables fast mid-circuit measurement.

Abstract: Under suitable experimental conditions, some twisted graphene multilayers and transition-metal dichalcogenides become Chern insulators, exhibiting the anomalous quantum Hall effect and orbital magnetization due to spontaneous valley polarization. We study (theoretically) the interaction of a Chern insulator with circularly polarized light, originating from the optical Stark energy shift. The interaction energy contains an antisymmetric term that couples the helicity of incident light and the Berry curvature of the electronic system.

Abstract: Topological mixed quantum states in or out of equilibrium can arise in open quantum systems. Their linear responses are generally non-quantized, even though quantized topological invariants can be defined. In this talk, I will present a real-time U(1) topological gauge field action capable of reconciling this paradoxical phenomenology. In addition to non-quantized linear responses, this action encodes quantized non-linear responses associated with mixed state topology.

Committee:Prof. Christopher Monroe  (Chair)Prof. Ronald WalsworthProf. Donald YeungProf. Norbert LinkeProf. Christopher Jarzynski (Dean’s Representative)

Dissertation Committee Chair: Prof. Steven Rolston
Committee: 
Dr. Trey Porto – Advisor – Co-Chair
Dr. Gretchen Campbell
Dr. Victor Galitski
Dr. Thomas Murphy (Dean’s Representative)

Abstract: Motivated by the recent progress of quantum chaos and quantum information scrambling, the growth of an operator under the Heisenberg evolution has attracted a lot of attentions. I will first introduce a recently proposed perspective on the operator growth problem from the Lanczos algorithm point of view and the associated “Krylov complexity”. While reviewing some of the recent results of Krylov complexity of the chaotic systems and integrable systems by other researchers, I will touch on our results about the  “Krylov complexity” of the many-body localization (MBL) systems.

Abstract: Why do chaotic quantum many-body systems thermalize internally? The eigenstate thermalization hypothesis (ETH) explains why if the Hamiltonian lacks degeneracies. If the Hamiltonian conserves one quantity ("charge"), the ETH implies thermalization within an eigenspace of the charge—in a microcanonical subspace. However, quantum systems can have charges that fail to commute with each other and so share no eigenbasis; microcanonical subspaces may not exist. Worse, the Hamiltonian will have degeneracies, so the ETH need not imply thermalization.

Abstract: The SpooQy-1 project designed, built and operated a source of polarisation entangled photon-pairs onboard a CubeSat for over 600 days. From the lessons learned in the SpooQy-1 mission, the Singapore-based team is working towards performing entanglement distribution from a small satellite to ground receivers. In this talk, I will share observations about the performance of the satellite, the entangled photon source, and the single photon detectors in orbit. These data has been used to validate some very useful models for predicting the effect of radiation on components.

Karmela Padavic-Callaghan is a science writer reporting on physics, materials science and quantum technology for New Scientist. Karmela earned a PhD in theoretical condensed matter physics and atomic, molecular, and optical physics from the University of Illinois Urbana Champaign and her research has been published in peer reviewed journals including Physical Review Letters and New Journal of Physics.
 

Dissertation Committee Chair: Professor Maissam Barkeshli

Committee:     

Professor Sankar Das Sarma          

Professor Jay Deep Sau

Professor Michael Gullans

Professor Mohammad Hafezi