Theoretical Research And Analysis Of DPSK Quantum Key Distribution System

Quantum cryptography, which is a combination of quantum mechanism and cryptology, solves the dilemma of the classical cryptography and has been developed as one of the most popular information technologies in the world. The security of quantum cryptosystems is guaranteed by the fundamental laws of quantum mechanism: the uncertainty principle and the non-cloning theorem, so we should not worry about eavesdropping when the quantum key distribution is operated in a public channel.Here we studied three main quantum key distributions which are most popular nowadays. And possible attacks towards these three protocols are also discussed, for example: the beam splitter attack and intercept-resend attack. The security of the DPSK protocol is mainly focused. As a result, the DPSK protocol is much stronger against the possible attack.In the quantum key distribution, the single photon detector is a very important component. Two kind of single photon detectors such as the InGaAs/InP APD and the up-conversion detector are discussed. The comparison of these two detectors is made. From the simulation result, it is proved that the performance of up-conversion detector is much better than the conventional detector.Finally, the expressions of secure communication rate of three protocols are given based on the possible attack. Moreover, from these formulations, the performances of three protocols are compared. Then we found that a secure communication rate of two orders of magnitude higher than before is possible. And when the up-conversion detector is applied, the communication distance is two times longer than before. Furthermore, the importance of the implemented protocol was illustrated, and the impact of Eve's allowed capabilities was investigated. It is concluded that the simple and efficient DPSK protocol allows for more than 200km of secure communication distance with high communication rates.