IQIM Postdoctoral and Graduate Student Seminar

Friday, September 22, 2023
12:00pm to 1:00pm
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East Bridge 114
Noise, complexity, and information dynamics in quantum circuits
Tommy Schuster, Sherman Fairchild Postdoctoral Scholar, Preskill Group,

Abstract: Quantum computers are believed to yield exponential advantages over their classical counterparts for certain tasks. However, near-term quantum devices are inevitably impacted by noise. I will discuss two recent works that leverage ideas from quantum information dynamics to understand the effect of noise. First, I will introduce a framework based on operator spreading to describe noise propagation in ergodic many-body systems. I will show that noisy systems exhibit universal classes of information dynamics that differ from unitary systems, providing a potential explanation for recent NMR experiments on ~100's of interacting quantum spins. Second, moving beyond physical systems, I will provide a provably efficient classical algorithm for simulating expectation values in almost any noisy quantum circuit. As a corollary, this establishes that almost any quantum experiment that provides an exponential speed-up over classical computation must fail in the presence of a noise rate greater than ~1/n, where n is the number of qubits.

Lunch will be provided, following the talk, on the lawn north of the Bridge Building.

For more information, please contact Marcia Brown by phone at 626-395-4013 or by email at