Electromagnetic waves with polarization modulation are widely utilized in Radar and Lidar,
depending on classical mechanics and Shannon information theory. In this paper, a quantum
detection system using polarized photons has been studied on theory and experiments based on the
laws of quantum electrodynamics. We give emphasis on the limits: standard quantum limit(SQL)
and quantum limit (QL) for target detection. Two sets photons of orthogonal 653nm linearly
polarized beams: 0°,90°,45° and 135° transmit to the target,and detect the scattered photons 5.7
meters away. Transmitter and Receiver synchronize their clocks to suppress the noise by the time
filtering.For some targets, our system can achieve utterly confidential target detection in theory.