Research About The Implementation Of Quantum Secure Communication Based On Optical Fiber Communication

With the development of the information age, information security is getting more and more importance. People pay more and more attention to the security of their communication. The security of classical secure communication is based on the difficulty of decomposition of large number. Limited by the manufacturing technology and physical properties of large scale integrated circuit computer almost can’t Crack the key. But now quantum computer is coming, whose computing speed is more than one thousand times than electronic computers’. The decomposition of large number is easy to solve by quantum computer, which means the classical communication is no longer safe. In order to resist the threat by it, quantum secure communication arises at the historic moment.Quantum cryptography communication includes quantum key distribution, quantum secret sharing, quantum secure communication, quantum dense coding and so on, which is a big family. According to the difference of information carrier, it can be divided into continuous variable quantum cryptography communication and discrete variable quantum cryptography communication. Because the strict implement conditions of discrete variable, such as single photon counter and single photon source, more and more attention is paid on continuous variable quantum communication, which is easier to implement.Our work is most concentrated on continuous variable quantum key distribution and continuous variable quantum dense coding. Continuous variable quantum key distribution uses the quantum property to distribute secure key, which is a secure method in theory. Due to the actual devices is not quite as perfect as theoretical model, which may introduce some security loopholes. We find the Faraday rotation mirror could affect the actual system key rate and transmission distance. We optimize the theoretical analysis model of continuous variable quantum key distribution. On this basis, we put forward some methods to reduce the influence of Faraday rotation mirror on the system.The second innovation point is the study of the environment’s influence on the continuous variable quantum dense coding. Continuous variable quantum dense coding uses continuous variables to realize high density of information transmission. Entanglement is frequently used as information carrier. System and environment would inevitably have interaction with each other, which will leads to annihilation of entanglement, thereby reducing the performance of the system. This paper studies the evolution of entangled state under the effect of different environmental situation, and its influence on continuous variable quantum dense coding mutual information. On this basis, the paper puts forward a method changing the transmittance of beam splitter to improve the mutual information.