Interpreting quantum discord through quantum state merging

TL;DR

This paper offers an operational interpretation of quantum discord by linking it to the additional quantum communication cost in state merging when prior information is ignored, providing insights into quantum correlations.

Contribution

It introduces a novel operational meaning of quantum discord through quantum state merging, connecting it to quantum communication costs and entropy properties.

Findings

Quantum discord equals the extra cost in quantum communication during state merging when ignoring prior info.

Provides operational interpretations for local purity and quantum deficit.

Discusses validity of the interpretation in single-copy scenarios.

Abstract

We present an operational interpretation of quantum discord based on the quantum state merging protocol. Quantum discord is the markup in the cost of quantum communication in the process of quantum state merging, if one discards relevant prior information. Our interpretation has an intuitive explanation based on the strong subadditivity of von Neumann entropy. We use our result to provide operational interpretations of other quantities like the local purity and quantum deficit. Finally, we discuss in brief some instances where our interpretation is valid in the single copy scenario.