Quantum illumination with multiple entangled photons
In this work, a theoretical generalization of Lloyd's quantum illumination to signal beams described by two entangled photon states is developed. It is shown that the new protocol offers a method to find the range of the target, reduces the size of the required time-bandwidth product to have the same signal to noise ratio than in Lloyd's quantum illumination, has a lower probability of false positive and is resilient against noise and also potentially against losses. However, the generation of the required three photon states for the protocol posses a technical problem for its practical implementation not fully addressed. Recent advances in triple photon generation that can overcome this problem are discussed. Other issues related with the protocol are also considered.