Research On Quantum Key Distribution Based On BB84 Protocol With One Single Photon Detector

The security of classical cryptosystem,which is depended on computational complexity,is threatened by quantum computer and quantum algorithm in cryptography.But,quantum key distribution based on fundamental laws of quantum mechanics has become the hotspot of communication research realm because of its unconditional security.However,quantum key distribution system with four single photon detectors has security vulnerability because of the detection efficiency mismatch of different single photon detector.In addition,the cost of quantum key distribution system is high because of expensive single photon detector.A quantum key distribution system was designed using time-multiplexing with one single photon detector in this dissertation.The quantum key distribution system based on BB84 protocol with polarization coding using four single photon detectors was discussed.The electrical hardware,time division multiplexer and four detecting gates of polarization light in the synchronization pulse of receiver were designed.The time of different polarization light intervals 30 ns successively by adding 6m optical fiber in corresponding different polarization light path of time division multiplexer.The synchronous calibration algorithm was designed.And it can calibrate four relative time positions of polarization light,and take it as detecting gate to distinguish different polarization light.The safety of the quantum key distribution system with one single photon detector was analyzed.And the analysis result showed this system can resist intercept-resent attack and time-shift attack.The system was successfully applied in indoor experiment.The experiment result showed that the rate of the system was up to 2.225 Kbps and the quantum bit error rate was less than 3% in the 0.1 mean photon number.