Local witness for bipartite quantum discord

TL;DR

This paper details a method for detecting quantum discord in bipartite systems using only local measurements and applies it to complex physical models, including thermal states and random Hamiltonians.

Contribution

It elaborates on a previously proposed local detection method for quantum discord and extends its application to generic complex systems and thermal equilibrium states.

Findings

Effective detection of quantum discord with local measurements

Performance analysis on random Hamiltonians and thermal states

Formulation of an ergodicity-like hypothesis for system analysis

Abstract

Recently, we proposed a method for the local detection of quantum correlations on the basis of local measurements and state tomography at different instances in time [Phys. Rev. Lett. 107, 180402 (2011)]. The method allows for the detection of quantum discord in bipartite systems when access is restricted to only one of the subsystems. Here, we elaborate the details of this method and provide applications to specific physical models. In particular, we discuss the performance of the scheme for generic complex systems by investigating thermal equilibrium states corresponding to randomly generated Hamiltonians. Moreover, we formulate an ergodicity-like hypothesis which links the time average to the analytically obtained average over the group of unitary operators equipped with the Haar measure.