The Characteristic Study Of Single Photon Source In Quantum Communication

Quantum communication can provide a new way for transmitting message securely and be applied in many fields, such as military, diplomacy and commerce. For example, quantum key distribution (QKD) solves the problem of unconditional key distribution. With the rapid development of QKD in nearly three decades, it has begun to be applied in the real world. The main security of quantum key distribution has been widely proved when considering the ideal system, which means that the source is the perfect single photon source, the classical channel has been authenticated with unconditional secure authentication protocol and so on. Unfortunately, due to the limitation of technical there is always appear multi-photon events, and the number of data-set size in practical QKD protocol is always finite, which will affect the results of QKD experiment. In this paper, we will focus on the security analyze of practical quantum key distribution.The paper is composed of six chapters. The first chapter is mainly introduces the history and latest progress of quantum communication. The second chapter introduces the basic theories of quantum mechanics and quantum communication. In chapter three, we firstly analysis several kinds of QKD protocols, then introduce the photon-number-splitting (PNS) attack, and give an important decoy-state method to combat the PNS attack in the last. In the chapter four, we introduced several methods to produce single photon at first, and then analysis the statistical feature of the weak laser pulse's photon number. In chapter five, we take weak coherent pulses as the QKD's source, considering the statistical fluctuations for the yield and error of the quantum state with finite code length, and then a general formula about the key generation rate of this protocol with statistical fluctuation was derived. At last, the numerical simulation results were obtained by using this formula. Finally, in chapter six, we summarize the work of this paper and make an expectation of the future in this field.