Easing the experimental requirements of quantum illumination

Quantum illumination is one of the main paradigms for implementing quantum radar in the low-frequency spectrum. Here, we discuss how to ease the open-air application of the protocol. I first define an experimentally feasible receiver for an entangled signal-idler transmitter. This consists of measuring heterodyne the received signal and adaptively measuring homodyne the idler, reaching a maximal quantum advantage of 3 dB in the error probability exponent with respect to the optimal classical strategy. Our receiver requires only a single tunable JPA. To relax the bandwidth requirement at the transmitter level, we discuss a sequential protocol that uses patches of modes sequentially to probe the target region. We show that, in a practical scenario, the sequential protocol needs two orders of magnitude less bandwidth with respect to the non-sequential protocol, while keeping the same quantum advantage. We finally briefly discuss possible applications of quantum illumination for backscatter communication and covert communication.