Concurrence in Disordered Systems

TL;DR

This paper develops a method to calculate disorder-averaged entanglement measures, like concurrence, in disordered quantum systems at finite temperatures, and demonstrates that disorder can enhance entanglement in certain regimes.

Contribution

It introduces a thermal perturbation theory approach to compute disorder-averaged concurrence, applicable to various entanglement measures in disordered quantum systems.

Findings

Disorder can increase concurrence in specific parameter regimes.

The method applies to XX spin chains and potentially other models.

Entanglement measures can be effectively computed in disordered, finite-temperature systems.

Abstract

Quantum systems exist at finite temperatures and are likely to be disordered to some level. Since applications of quantum information often rely on entanglement, we require methods which allow entanglement measures to be calculated in the presence of disorder at non-zero temperatures. We demonstrate how the disorder averaged concurrence can be calculated using thermal many-body perturbation theory. Our technique can also be applied to other entanglement measures. To illustrate, we find the disorder averaged concurrence of an XX spin chain. We find that concurrence can be increased by disorder in some parameter regimes.