Quantum illumination versus coherent-state target detection

TL;DR

Quantum illumination, initially thought to outperform classical methods in noisy environments, may not surpass coherent-state detection in the single-photon regime and could be less effective, though it shows promise outside this regime.

Contribution

This paper critically evaluates the performance of quantum illumination in the single-photon regime, challenging previous claims of its superiority over classical methods.

Findings

Quantum illumination is at best equal to coherent-state detection in the single-photon regime.

Quantum illumination can be substantially worse than classical methods in this regime.

Performance gains are possible outside the single-photon regime, as previously shown.

Abstract

Lloyd [1] proved that a large performance gain accrues from use of entanglement in single-photon target detection within a lossy, noisy environment when compared to what can be achieved with unentangled single-photon states. We show that the performance of Lloyd's "quantum illumination" system is, at best, equal to that of a coherent-state transmitter, and may be substantially worse. Nevertheless, as shown in [2], quantum illumination may offer a significant performance gain when operation is not limited to the single-photon regime.