Security Research Of Quantum Key Distribution System Based On Practical Devices

The research of quantum information has shown that if one encodes messages onto quantum states, he will be able to achieve a perfect cryptographic communication whose security is unconditionally guaranteed by the well-known uncertainty principle of quantum mechanics. This technique is called quantum cryptography or quantum key distribution.The main purpose of this work is to study the security, high efficiency single photon detection circuits, and analyze the security of quantum key distribution system. Our aim is to explore novel schemes and techniques for potentially practical quantum cryptography. Finally we finished the security analysis work to the long-distance quantum cryptosystem with long-term stability.On the security analysis of quantum key distribution system. The single-photon sources used in most practical QKD systems are simply an attenuated weak laser pulse. It is not perfect single-photon source, but is quasi-single-photon source which follows Poissonian distribution. The probability of every nonempty light pulse containing multiphoton is nonzero, the powerful eavesdropper (Eve) can take advantage of this to obtain some information about the final key. So it is necessary to study the security aspects of the practical QKD system. Using Shannon's information theory, calculating the information gained by Eve and legal receiver Bob individually. Finishing the security analysis of 50.6 km long distance stable quantum key distribution system. The mean photon we used was less than 0.1 and the overall error rate of quantum key was only 4%, the whole system can stably work over more than 12 hours. Suppose, Eve launches photon-number-splitting (PNS) attack on multiphoton signals, and optimal attack (OA) on single-photon signals, adopting Shannon's information theory to analyze the security of the practical QKD system based on weak coherent light. The research result shows that the practical QKD system is secure under the attacks of PNS and OA, and the upper bound of the error rate that the legitimate users (Alice and Bob) can tolerate is also derived from our study.On single photon detection, in order to reduce the dead time and enhance the counting rate of single photon detector, a flexible and chronometrical circuit is...