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.
We propose a novel synchronization scheme using a periodic light pulse for free-space quantum key distribution (QKD)
system. For our 10MHz system, the repetition rate of timing pulse in the novel synchronization scheme can be reduced to
100 KHz or even lower. It allows employing a KHz repetition rate ultrashort pulse laser as timing synchronization source
to implement high precision time synchronization. In this paper, short term time drift induced by atmospheric turbulence
is analyzed, and how the time deviation impacts on the final secure key generation rate in our QKD system is calculated.
In addition, we carried out the QKD experiments over the distance of 1.38 km. The results of the experiments indicate
that our scheme is feasible.
We presented an advanced design of receiver in free space quantum key distribution (QKD) system based on BB84
protocol. In this system, a novel four polarization beam splitter is used in the receiver. It simplifies the receiver
fabrication process, and the reflection loss is reduced too. Then we built the transmitter and the receiver for QKD system.
The outdoor 200m free space QKD experiment was carried out, the bit error rate is 0.91% when the average photon
number in each optical pulse was about 0.1. This result indicates that our design for the QKD system is feasible.