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 article, 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.

中文翻译：

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用于量子照明的噪声接收器

量子照明（QI）有望在目标检测中取得前所未有的性能，但其实施存在各种问题。在目标测距是一个问题的情况下，信号和闲散重组构成了协议成功的关键障碍。如果在空闲模式上执行测量仍然可以产生量子优势，那么这可能会得到缓解。在本文中，我们研究了通用相关高斯源的 QI 协议，并研究了相位共轭 (PC) 接收器，根据信号和空闲能量及其互相关推导出相关的 SNR，这些可以很容易地进行调整合并由于高斯测量而增加的噪声。我们确认在空闲模式上执行的外差测量会导致性能，它渐近地接近具有零差检测的相干状态。然而，如果信号模式受外差影响但空闲模式保持干净，则性能将逐渐接近 PC 接收器的性能，而不会增加任何噪声。