Bound for Gaussian-state Quantum illumination using direct photon measurement

TL;DR

This paper derives analytic bounds for Gaussian-state quantum illumination using photon detection methods, showing how different states and detection schemes affect performance in signal-to-noise ratio evaluations.

Contribution

It provides new analytic bounds for quantum illumination with Gaussian states using on-off and PNR detection, comparing performance of different states and measurement strategies.

Findings

TMSV state outperforms coherent and CCT states in coincidence counting.

Coherent state can outperform TMSV with higher photon number in on-off detection.

PNR detection on signal mode with on-off on idler mode achieves near-optimal performance.

Abstract

It is important to find feasible measurement bounds for quantum information protocols. We present analytic bounds for quantum illumination with Gaussian states when using an on-off detection or a photon number resolving (PNR) detection, where its performance is evaluated with signal-to-noise ratio. First, for coincidence counting measurement, the best performance is given by the two-mode squeezed vacuum (TMSV) state which outperforms the coherent state and the classically correlated thermal (CCT) state. However, the coherent state can beat the TMSV state with increasing signal mean photon number in the case of the on-off detection. Second, the performance is enhanced by taking Fisher information approach of all counting probabilities including non-detection events. In the Fisher information approach, the TMSV state still presents the best performance but the CCT state can beat the TMSV state with increasing signal mean photon number in the case of the on-off detection. Furthermore, we show that it is useful to take the PNR detection on the signal mode and the on-off detection on the idler mode, which reaches similar performance of using PNR detections on both modes.