Quantum revivals and many-body localization

TL;DR

This paper investigates how a single qubit's magnetization exhibits periodic revivals in a disordered spin chain, revealing differences between many-body localized and ergodic phases through observable revival suppression.

Contribution

It demonstrates that quantum revivals serve as a measurable indicator of many-body localization, providing an alternative to entanglement growth for characterizing non-ergodic phases.

Findings

Revivals occur in the localized regime but are suppressed by interactions.

The ergodic phase shows no revivals, acting as a bath.

Revival suppression quantifies non-ergodic behavior.

Abstract

We show that the magnetization of a single `qubit' spin weakly coupled to an otherwise isolated disordered spin chain exhibits periodic revivals in the localized regime, and retains an imprint of its initial magnetization at infinite time. We demonstrate that the revival rate is strongly suppressed upon adding interactions after a time scale corresponding to the onset of the dephasing that distinguishes many-body localized phases from Anderson insulators. In contrast, the ergodic phase acts as a bath for the qubit, with no revivals visible on the time scales studied. The suppression of quantum revivals of local observables provides a quantitative, experimentally observable alternative to entanglement growth as a measure of the `non-ergodic but dephasing' nature of many-body localized systems.