Overarching framework between Gaussian quantum discord and Gaussian quantum illumination

TL;DR

This paper demonstrates that quantum discord is the key resource enabling quantum advantage in Gaussian quantum illumination by comparing information bounds obtained with EPR and coherent probes.

Contribution

It establishes a direct link between Gaussian quantum discord and the quantum advantage in illumination, providing a theoretical framework for understanding the resource.

Findings

Holevo information bounds are calculated for EPR and coherent probes.

Quantum advantage is approximately equal to the discord consumed during encoding.

Results are exact in low reflectivity and low energy regimes.

Abstract

We cast the problem of illuminating an object in a noisy environment into a communication protocol. A probe is sent into the environment, and the presence or absence of the object constitutes a signal encoded on the probe. The probe is then measured to decode the signal. We calculate the Holevo information and bounds to the accessible information between the encoded and received signal with two different Gaussian probes---an Einstein-Podolsky-Rosen (EPR) state and a coherent state. We also evaluate the Gaussian discord consumed during the encoding process with the EPR probe. We find that the Holevo quantum advantage, defined as the difference between the Holevo information obtained from the EPR and coherent state probes, is approximately equal to the discord consumed. These quantities become exact in the typical illumination regime of low object reflectivity and low probe energy. Hence we show that discord is the resource responsible for the quantum advantage in Gaussian quantum illumination.