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Register a new userQuantum illumination with noisy probes: Conditional advantages of non-Gaussianity
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Entangled states like two-mode squeezed vacuum states are known to give quantum advantage in the illumination protocol, a method to detect a weakly reflecting target submerged in a thermal background. We use non-Gaussian photon-added and subtracted states as probes for the single-shot quantum illumination both in the presence and absence of noise. Based on the difference between the Chernoff bounds obtained with the coherent state and the non-Gaussian state having equal signal strengths, whose positive values are referred to as a quantum advantage in illumination, we classify the performance of non-Gaussian states, when photons are added (subtracted) in (from) a single mode or in (from) both the modes. We highlight the hierarchy among Gaussian and non-Gaussian states obtained via this method, which is compatible with correlations per unit signal strength. Interestingly, such hierarchy is different when comparisons are made only using the Chernoff bounds. The entire analysis is performed in presence of different noisy apparatus like faulty twin-beam generator, imperfect photon addition or subtraction as well as with noisy non-Gaussian probe states.
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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 protocols 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.
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