Noisy receivers for quantum illumination

TL;DR

This paper analyzes the performance of phase-conjugating receivers in quantum illumination with noisy measurements, showing that certain heterodyne detection schemes can approach optimal target detection performance.

Contribution

It derives the SNR for Gaussian sources with phase-conjugating receivers under noisy measurement conditions, revealing how heterodyne detection impacts quantum advantage.

Findings

Heterodyne measurement on the idler mode approaches coherent state performance.

Maintaining a noise-free idler mode with heterodyne detection yields optimal asymptotic performance.

The analysis incorporates added Gaussian noise into the measurement model.

Abstract

Quantum illumination (QI) promises unprecedented performances in target detection but there are various problems surrounding its implementation. Where target ranging is a concern, signal and idler recombination forms a crucial barrier to the protocol's success. This could potentially be mitigated if performing a measurement on the idler mode could still yield a quantum advantage. In this paper we investigate the QI protocol for a generically correlated Gaussian source and study the phase-conjugating (PC) receiver, deriving the associated SNR in terms of the signal and idler energies, and their cross-correlations, which may be readily adapted to incorporate added noise due to Gaussian measurements. We confirm that a heterodyne measurement performed on the idler mode leads to a performance which asymptotically approaches that of a coherent state with homodyne detection. However, if the signal mode is affected by heterodyne but the idler mode is maintained clean, the performance asymptotically approaches that of the PC receiver without any added noise.