UChicago PME Quantum Science and Engineering Seminar - Thomas Schuster

Physics and Complexity in a Growing Quantum World

Modern quantum experiments achieve coherences and scales once only dreamed of, pushing the limits of physics and computation. To understand and guide these advances, the questions we ask of quantum mechanics today---centered around the behavior of information and complexity in large coherent physical systems---differ essentially from those asked in the past. In this talk, I will present two examples drawn from my work in which remarkably simple ideas regarding the dynamics of quantum information in many-body systems provide a unifying lens for answering these questions. First, I will present a provably-accurate classical algorithm to simulate noisy quantum circuits in time growing only polynomially in the system size. Our algorithm builds upon physical concepts from quantum information dynamics, and establishes strict fundamental limits on the magnitude of advantage that quantum experiments with uncorrected noise can achieve. Second, I will discuss the onset of universal random matrix behaviors in locally-interacting quantum circuits and time dynamics. I will show that local quantum dynamics can become indistinguishable from completely random processes in exponentially shorter times than previously thought, with broad applications in quantum device benchmarking, cryptography, and physics. I will conclude by looking forward, and discuss several essential open questions at the interface of complexity, physics, and quantum computing and simulation experiments. 

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