Weak measurements and nonClassical correlations

TL;DR

This paper extends quantum discord to include weak measurements, showing that weak discord often matches normal discord and discussing its implications for understanding quantum correlations.

Contribution

It introduces the concept of weak quantum discord, generalizing quantum discord to weak measurements and analyzing its properties across different quantum states.

Findings

Weak discord often equals normal discord in many cases.

Weak discord reduces to normal discord in certain limits.

The study discusses implications for interpreting quantum correlations.

Abstract

We extend the definition of quantum discord as a quantifier of nonClassical correlations in a quantum state to the case where weak measurements are performed on subsystem $A$ of a bipartite system $AB$. The properties of weak discord are explored for several families of quantum states. We find that in many cases weak quantum discord is identical to normal discord and in general the values of the two are very close to each other. Weak quantum discord reduces to discord in the appropriate limits as well. We also discuss the implications of these observations on the interpretations of quantum discord.