Observation of thermalization and information scrambling in a superconducting quantum processor

TL;DR

This study demonstrates quantum thermalization and information scrambling in a superconducting qubit ladder, contrasting with non-thermalizing behavior in a 1D chain, thus advancing understanding of non-equilibrium quantum dynamics.

Contribution

First experimental observation of thermalization and scrambling phenomena in a superconducting quantum ladder system, highlighting differences with integrable models.

Findings

Quantum thermalization observed in the $XX$ ladder.

Information scrambling confirmed via tripartite mutual information.

The 1D $XX$ chain does not thermalize or scramble information.

Abstract

Understanding various phenomena in non-equilibrium dynamics of closed quantum many-body systems, such as quantum thermalization, information scrambling, and nonergodic dynamics, is a crucial for modern physics. Using a ladder-type superconducting quantum processor, we perform analog quantum simulations of both the $XX$ ladder and one-dimensional (1D) $XX$ model. By measuring the dynamics of local observables, entanglement entropy and tripartite mutual information, we signal quantum thermalization and information scrambling in the $XX$ ladder. In contrast, we show that the $XX$ chain, as free fermions on a 1D lattice, fails to thermalize, and local information does not scramble in the integrable channel. Our experiments reveal ergodicity and scrambling in the controllable qubit ladder, and opens the door to further investigations on the thermodynamics and chaos in quantum many-body systems.