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Q-FARM Presents a Double Feature Seminar - " Memory and optimization with multimode cavity QED" & "Transverse-Field Ising Dynamics by Rydberg Dressing in a cold atomic gas"

Event date: 
Wednesday, May 12, 2021 - 12:45 pm
Brendan Marsh & Ognjen Marković (Stanford University)

Talk Title#1 : Memory and optimization with multimode cavity QED

Speaker#1: Brendan Marsh


Abstract#1 : Quantum systems are driving a revolution in computing and information theory. Driven-dissipative quantum systems, which are both pumped by an external source and are open to environmental interactions, have not been explored as a computational resource as fully as their closed counterparts. In this talk, I will describe how a driven-dissipative system is realized by coupling ultracold atoms to a multimode optical cavity and how it can perform various computational tasks. Through a combination of unitary and dissipative dynamics, the system can learn and recognize arbitrary sets of patterns, an ability known as associative memory, and also functions as a heuristic solver for (NP hard) Ising optimization problems. These functionalities can be understood in terms of semiclassical theories that describe the transition to a superradiant ordered state, which encodes a learned pattern or a solution to an Ising problem. While a fully quantum description remains intractable, experimental progress will be discussed that demonstrates the required ingredients for near-term realization. 


Talk title #2: Transverse-Field Ising Dynamics by Rydberg Dressing in a cold atomic gas

Speaker#2:  Ognjen Marković
Abstract #2

With recent progress on building large and controllable quantum systems, we are on the cusp of harnessing these systems for quantum computation and metrology. Optically controlled interactions are a necessary tool to implement computation and metrology schemes in a system of cold atoms. In this talk, we will present a realization of long-range optically-controllable Ising interactions in a cold gas of cesium atoms by Rydberg dressing. By adding microwave coupling between the clock states we emulate the transverse-field Ising model and detect dynamical signatures of the paramagnetic-ferromagnetic phase transition. We will discuss current progress towards producing spin squeezing by using local and dynamical control of interactions. Finally, we will describe prospects of encoding a quantum algorithm in a hardware-efficient way in this system.



Bio: Brendan Marsh is a Ph.D. student in Professor Benjamin Lev’s research group at Stanford University. He investigates light-matter interactions in many-body quantum systems and explores their use as a computational resource. His work more generally includes experimental quantum optics and theoretical methods to describe open quantum systems. He received a master’s degree in applied mathematics and theoretical physics from the University of Cambridge in 2018 and a B.S. in physics and mathematics from the University of Missouri in 2017.


Bio: Ognjen Marković is a physics Ph.D. candidate in the Schleier-Smith lab at Stanford University. He is working on a cold atom experimental platform with applications ranging from quantum simulation to quantum metrology. He obtained his B.A. and M.Sci. degrees in Natural Sciences at the University of Cambridge.