How to calculate quantum quench distributions with a weighted Wang-Landau Monte Carlo

TL;DR

This paper extends the Wang-Landau Monte Carlo method to accurately estimate full probability distributions of observables after a quantum quench in large systems, especially when full enumeration is infeasible.

Contribution

The authors develop a weighted Wang-Landau Monte Carlo approach for quantum quenches, enabling precise distribution estimates in large disordered systems where traditional methods struggle.

Findings

Generalized Gibbs ensemble fails in disordered systems

Method accurately captures long-time observable distributions

Applicable to large free-fermion models with disorder

Abstract

We present here an extension of the Wang-Landau Monte Carlo method which allows us to get very accurate estimates of the full probability distributions of several observables after a quantum quench for large systems, whenever the relevant matrix elements are calculable, but the full exponential complexity of the Hilbert space would make an exhaustive enumeration impossible beyond very limited sizes. We apply this method to quenches of free-fermion models with disorder, further corroborating the fact that a generalized Gibbs ensemble fails to capture the long-time average of many-body operators when disorder is present.