Response of a quantum disordered spin system to a local periodic drive

TL;DR

This paper investigates how a disordered quantum spin chain responds to a local periodic drive, using fidelity susceptibility to distinguish between many-body localized and ergodic phases, with implications for quantum simulation.

Contribution

It introduces the use of fidelity susceptibility distributions to identify phases in a disordered spin system under local periodic driving, applicable to quantum networks.

Findings

Fidelity susceptibility exhibits long tails in the many-body localized phase.

Average susceptibility decreases rapidly with increasing disorder in the localized phase.

Susceptibility distribution is narrow and weakly dependent on disorder in the ergodic phase.

Abstract

We consider a one-dimensional spin chain system with quenched disorder and in the presence of a local periodic drive. We study the time evolution of the system in the Floquet basis and evaluate the fidelity susceptibility, which is a measure of how a given state changes under a small perturbation, of states to a weak periodic drive. We demonstrate that the statistical properties of the fidelity susceptibility over different disorder realizations can be used to identify two phases of the system: (1) the many-body localized phase, in which the susceptibility exhibits long tails while its average value decreases rapidly as disorder increases; and (2) the ergodic phase, in which the susceptibility distribution is narrow and its average value weakly depends on disorder. This distinction in the average value of the susceptibility between the two phases develops readily for systems with ten or more spins. Therefore, recently built networks of qubits subject to a local drive can simulate dynamics of a system in the many-body localization regime. We also show that the spin accumulation speed is correlated with the fidelity susceptibility and can also be used to distinguish the two phases.