The Experimental Study Of Long Range Quantum Key Distribution System

Quantum information is a cross-field subject of quantum physics and classical information science, which has advantages compared to classical information technology. The security of Quantum Key Distribution (QKD) is guaranteed by physical laws, which solved the vital problem of key distribution in classical cryptography. QKD is a most applicable subject in quantum information science.QKD is studied in the theory and experiment field widely, and its real world security of QKD is accepted after the development of the decoy method. Currently, QKD is a mature subject, which is stepping from theory study, into experiment and further to engineering testing. Fiber, which is widely used in classical communication, has outstanding optical properties, is suitable to be used as quantum channel in QKD. Most reported QKD systems are using fiber as Quantum channel.In this thesis, the problems in building long range QKD systems are discussed, the experimental setup, analysis, and result is reported. The thesis analyzed the decoy-based QKD method, and optimized the parameters for different application scene. We designed the optical, physical, and the whole QKD system, discussed the process of designing a QKD system and the key points in it. We designed the post-processing software of QKD. The commonly used post processing method of authentication, error sifting, and privacy amplification is introduced. The adapting LDPC error sifting method is also developed. We built a phase-based system, and built a chain-like QKD net by trusted relay, realized the first quantum telephone network. We designed a polarization based QKD system, with this kind of sytem, we built a metropolitan optical transparent network by all optical switch. By optimizing the system, we realized long distance QKD up to200km. Based on this system, we built an applicable system with100km fiber length. Further more, we built an inter-city quantum network with the help of this system, including two inner-city network, and a trusted relay built in another city.We have built QKD systems, the technology enhancing its stability, performance is a foundation for future QKD systems. The QKD network proved the real world application of QKD system and QKD network is possible.