Partially reflecting jamming objects in correlation-enhanced target detection with entangled photons

In the optical detection of distant objects, one can benefit from quantum light properties over those of classical light. Two-beam correlation-enhanced protocols can improve imaging or target detection even under strong background noise and in the low photon flux regime. We demonstrate that a partially reflecting jamming object introduces noise to these protocols, including quantum illumination. In contrast to background noise, the signal radiation reflected from the jammer is correlated with the corresponding idler beam. We analyze the means to mitigate this noise and introduce an indistinguishability parameter μ, showing how efficiently the jammer can be distinguished from the target. We use the quantum Chernoff bound and the density matrix orthogonalization procedure to separate the contributions from the target, the background, and the jammer. We illustrate our findings with an experiment using optical entangled photon pairs at 800 nm. Our results can be applied to the design of target detection protocols and advanced imaging techniques.