Yaodong Li (Stanford University), QISE Seminar: Quantum codes in and out of equilibrium

Abstract

Quantum error-correcting (QEC) codes hold great technological potential. Furthermore, their study has provided fruitful inspiration for many-body physics. Here, we present two recent examples illustrating this connection. First, we propose a general relation between the threshold of quantum codes under local error channels and the equilibrium stability of the corresponding code Hamiltonian under local perturbations. We show that the success probability of the code can be used to upper bound the ground state splitting and lower bound the energy gap to local excitations. These results are particularly relevant for higher-dimensional spaces or general graphs, where such stability guarantees were previously unknown.
Second, we consider a setting more relevant to experimental quantum computing, involving error correction operations performed at a speed R. Unlike their zero-speed counterparts, error correction in this regime is described by a kinetic equation with a rate suppressed by exp(1/R), from which universal dynamic exponents can be extracted. We also identify a scaling function that describes the crossover between the kinetic behavior at R>0 and the equilibrium statistical mechanical model as R -> 0.

Bio

Yaodong Li will join UW in Fall 2026 as an Assistant Professor in the Department of Mechanical Engineering. His research interests lie at the intersection of quantum information and many-body physics. He has explored novel collective dynamics of non-equilibrium quantum systems, and seeks to advance the development of robust quantum information processors.