Super quantum discord for X-type states

TL;DR

This paper derives an analytical formula for super quantum discord in X-type two-qubit states, enhancing understanding of quantum correlations and their dynamics under nondissipative channels.

Contribution

The authors provide the first explicit analytical formula for super quantum discord in general X-type states, extending previous results for special cases.

Findings

Derived an explicit formula for SQD in X-type states

Compared SQD with normal quantum discord

Analyzed SQD dynamics under nondissipative channels

Abstract

Weak measurement is a new way to manipulate and control quantum systems. Different from projection measurement, weak measurement only makes a small change in status. Applying weak measurement to quantum discord, Singh and Pati proposed a new kind of quantum correlations called "super quantum discord (SQD)" [Annals of Physics \textbf{343},141(2014)]. Unfortunately, the super quantum discord is also difficult to calculate. There are only few explicit formulae about SQD. We derive an analytical formulae of SQD for general X-type two-qubit states, which surpass the conclusion for Werner states and Bell diagonal states. Furthermore, our results reveal more knowledge about the new insight of quantum correlation and give a new way to compare SQD with normal quantum discord. Finally, we analyze its dynamics under nondissipative channels.