Single-photon Quantum Key Distribution System, Theoretical Modeling And Analysis

Communication technology has been made a great progress with the development of relative hardware and theories. People attach their must attentions to the security and secrecy during the information transmitting. It is one of the key communication technologies on the aspects how to connect accurately the either sides or multi-sides in the communication and assure the information transmission to be secure and secret.In this paper, the author, under the full grasp of status of quantum cryptographic key research, does research concentrating on the terrestrial free space optical links and fiber links ,The quantum communication can be divided into two stages: In the first stage, the quantum communication is conducted and cryptographic key communication is finished through the quantum channel; In the second stage, the negotiation of cryptographic key is achieved in order to measure whether any bug exists or not, and then confirms the final cryptographic key, at this time the quantum communication is accomplished. The termless security of quantum cryptographic key protocol is based on the Quantum Non-clone principle and Heisenberg Uncertainty principie. Whilst, these two characteristics mentioned above contributes greatly to solve the problems of low transmitting rate, complicated operation and forge-identity assault in the BB84 protocol.Highly attenuated laser pulses with Poisson distribution are used as single-photon sources and the BB84 and B92 protocols are used for free- space quantum key distribution. By introducing the quantum channel transmission , the single-photon acquisition probability , the measuring factor and the sifting factor , the theoretical model of the quantum bit error rate was established and the expressions of the quantum bit error rate were given. The main factors that cause the quantum bit error rate are the optical elements , the detector dark noise and the space optical environment and these factors were analyzed. The quantum bit error rate was analyzed in the numerical simulation for the laser links between a ground station and a satellite in a low earth orbit . The results show that it is feasible to implement quantum key distribution between a ground station and a satellite in a low earth orbit and that it is the detector dark noise and the space optical environment that limit the link distance for free- space quantum key distribution.The influence of dispersion and loss on quantum bit error rate of a quantum key distribution systemis analytically studied via quantum SchrEdinger equation. The results show that the haul of quantum key distribution system can be increased by using the dispersion shift fiber and weak pulse with short pulse width in some wavelength...