Comparison of quantum discord and fully entangled fraction of two classes of $d\otimes d^2$ states

TL;DR

This paper compares quantum discord and fully entangled fraction in two classes of bipartite states, revealing their relationship and behavior, especially in maximally entangled and separable states.

Contribution

It introduces a comparison of quantum discord and fully entangled fraction for complemental classes of $d\otimes d^2$ states, extending understanding of their correlation properties.

Findings

Maximally entangled mixed states are also maximally discordant.

Separable-entanglement boundary appears as an inflection point in discord diagrams.

Quantum discord correlates with entanglement properties in the studied classes.

Abstract

The quantumness of a generic state is the resource of many applications in quantum information theory and it is interesting to survey the measures which are able to detect its trace in the properties of the state. In this work we study the quantum discord and fully entangled fraction of two classes of bipartite states and compare their behaviors. These classes are complements to the $d\otimes d$ Werner and isotropic states, in the sense that each class possesses the same purification as the corresponding complemental class of states. Our results show that maximally entangled mixed states are also maximally discordant states, leading to a generalization of the well-known fact that all maximally entangled pure states have also maximum quantum discord. Moreover, it is shown that the separability-entanglement boundary of a Werner or isotropic state is manifested as an inflection point in the diagram of quantum discord of the corresponding complemental state.