Optical ranging with quantum advantage and anti-stealth

Quantum illumination (QI) is implemented by a joint measurement between the idler field and the signal field reflected from the low-reflectivity stationary target in a noisy environment. The joint measurement is possible only with prior knowledge of the target's location, which is unknown in many cases. The technique described in this article overcomes this limitation by using optical entanglement and quantum cross-correlated homodyne measurement. This technique offers the following additional advantages in comparison with QI implementation through joint measurement: (1) quantum storage and prior knowledge about the target's distance are not required, (2) it adds ranging capability, and (3) it adds anti-stealth mechanism to suppress the low-reflectivity of the target. As the detection is at optical frequencies, the environment is considered as a stray laser, which could be a decoy, a jamming field, a probe field from another ranging application, or a field used to mask the actual probe. Thus, the environment considered in this Letter is suitable for ranging applications like lidar.