Implementation Of Polarization Control Algorithms Based On Polarization Encoding QKD System

Quantum communication is a new communication technology based on quantum mechanics characteristics and combines with the classical theory of communication. Heisenberg uncertainty principle and quantum state non-cloning theorem guarantee the unconditional reliability of quantum key distribution, and the quantum cryptography communication based on quantum key distribution is becoming the focus of people's study. Quantum cryptography communication's future application prospect has been overwhelming. The polarization information as the carrier of quantum cryptography communication has a direct impact on key rate of quantum key distribution system. This paper focuses on the realization of polarization control algorithm in quantum key distribution system based on polarization encoding.Firstly we introduce the basic theory of quantum mechanics, the present situation and prospect of quantum communication, including quantum bit, some quantum mechanical theories guaranteeing unconditional security of QKD namely quantum state non-cloning theorem and Heisenberg uncertainty principle, classical QKD protocol such as B92 protocol etc. Some basic concepts about optical polarization and polarization protocol principle are alse be describedSecondly, we analyze the change law of polarization state in the optical fiber transmission and studies the important influence of polarization loss on system key rate and bit error rate, by using random polarization mode dispersion modelThirdly, with Jones vector and Poincare representations, squeeze-fiber PC has been modeled and analyzed based on the research of polarization characteristics of optical pulse and the common principle of polarization control model, then we propose a polarization control algorithm. The proposed algorithm achieve the optimal polarization location rapidly by using the detector to detect the single photon count as feedback and applying an improved genetic algorithm to the preparation phase of single photon polarization state in QKD system. The workflow of genetic algorithm and its improvement are introduced, then we simulate and analyze the implementation of algorithm in system.Besides, based on small amplitude of QKD polarization loss simulated annealing algorithm has been used to compensate the polarization direction and to implement real-time regulation of QKD system according to bit error rate of QKD system.we give a detailed description of algorithm model and the specific process of the algorithm, and the simulation of quantum key distribution system under various parameters is carried out. By comparison with the results, we determine the optimal parameters. Experimental results show that simulated annealing algorithm is able to adjust the polarization to suitable range and has a reliable real-time adjustment abilityFinally, we summarize the paper and give some suggestion for the further research. Next step, we will need to study the effect of polarization mismatch on information security. According to the actual controller type, we need to do some experiments to verify the amount of time during the offset move. Then we need to select the appropriate control parameters, doing many experiments in the operation of actual polarization encoding QKD system to verify the actual application effect of algorithm and the influence of every parameter on polarization effect.