Experimental Quantum Target Detection Approaching the Fundamental Helstrom Limit

Quantum target detection is an emerging application that utilizes entanglement to enhance the sensing of presence object. Although several experimental demonstrations for certain situations have been reported recently, single-shot limit imposed by Helstrom has not reached because unknown optimum measurements. Here we report demonstration quantum detection, also known as illumination, in single-photon limit. In our experiment, one photon maximally entangled pair employed probe signal and corresponding measurement implemented at receiver. We explore problem different regions parameter space verify advantage exists even a forbidden region conventional where all classical schemes become useless. Our results indicate illumination breaks up 40%, while approaching These only demonstrate but manifest its valuable potential detection.