Part Of Parameters Optimization And Simulation Of Optical Source And Detection In Quantum Key Distribution

Quantum key distribution produces and releases key by making use of quantum mechanics principle,to solve the insuperably limitation of key distribution in classical cryptography,and guarantees the absolute security of the cryptographic key. Quantum information is currently one of the hottest research fields in physics, and quantum key distribution (QKD) is the most advanced subfield so far with regard to practical application.This thesis first introduce background, key technique, theory developing, experiment realizing, experiment progresing of QKD. Ideal single-photon source is the critical technique of QKD, at present the single-photon source of QKD is obtained by laser emmited with strong attenuation,moreover mean photon number affects the probability of single-photon,so it is necessary to research the optimal mean photon number,For quantum cryptography, the optimal mean photon number(μ) is the average photon number per transmitted pulse that results in the highest delivery rate of distilled cryptography key bits,given a specific system scenario and set of assumptions about Eve's capabilities. Given the reasonable appraisal about Eve's capabilities,offered detailed eavesdropping model and defence function,and researched the optimal mean photon number using revised delivery rate of distilled key bits. Experimental results show,μ= 1.15 provides nearly 10 times the throuthout of systems that empoly μ=0.1, without any adverse affect on system security.The single photon detector performance quality has affected the quantum key distribution system quality and the effective transmitting distance directly. How selects and carries on the appraisal to the detector, has become the key factor, therefore this thesis proposed to research APD by using computer simulation. Under the suitable supposition premise and on the basis of the empirical formula, the field profile of separate absorption, grading, charge, and multiplication avalanche photodiode (SAGCM-APD) is calculated by means of the MATLAB matrix operation function. Theelectrons and holes multiplication coefficients are in turn computed. By using above coefficients and the transfer functions, the gain-voltage and the frequency-response characteristics for SAGCM-APD are figured out. There is a good correspondence between the simulation with experimental results.