Operational Significance of Discord Consumption: Theory and Experiment

TL;DR

This paper demonstrates experimentally that quantum discord, even without entanglement, can be used as a resource to encode and access information through coherent quantum interactions, revealing a new operational significance.

Contribution

It introduces an operational method to use quantum discord as a physical resource for information encoding and retrieval without entanglement.

Findings

Discord can be consumed to encode information inaccessible by classical means.

Coherent interactions recover additional information linked to discord consumption.

No entanglement is present at any stage of the experiment.

Abstract

Coherent interactions that generate negligible entanglement can still exhibit unique quantum behaviour. This observation has motivated a search beyond entanglement for a complete description of all quantum correlations. Quantum discord is a promising candidate. Here, we demonstrate that under certain measurement constraints, discord between bipartite systems can be consumed to encode information that can only be accessed by coherent quantum interactions. The inability to access this information by any other means allows us to use discord to directly quantify this `quantum advantage'. We experimentally encode information within the discordant correlations of two separable Gaussian states. The amount of extra information recovered by coherent interaction is quantified and directly linked with the discord consumed during encoding. No entanglement exists at any point of this experiment. Thus we introduce and demonstrate an operational method to use discord as a physical resource.