A quantum-illumination receiver is described comprising a phase-conjugation and mixing system for mixing and/or conjugating the idler beam from an entangled light transmitter and the return beam from the target to produce an output beam that is representative of the presence or absence of the target, a light beam collector for receiving a return light beam from the target region and directing the return light beam from a target region to the phase-conjugation and mixing system input, an optical input for receiving an idler light beam from a transmitter and directing the idler light beam from the transmitter to the phase-conjugation and mixing system, a sensor for measuring the output of the phase-conjugation and mixing system, and a processor to process the output of the sensor to make an determination about the presence of the target.