| Quantum key distribution is a new interdiscipline which was developed in this 30 years,combined with information theory and quantum theory.It has a feature of security without any conditions which was based on Heisenberg uncertainty principle and quantum no-cloning theorem.The whole progress is that Alice loads information on the single photon and transmits it among quantum channel to Bob.The main protocol of quantum key distribution is BB84 protocol,B92 protocol and so on.The development of multi-user quantum key distribution made quantum telecommunication technology come from lab research to practical application.The main contents of this study are as follows:It introduced the development history of classical cryptography and quantum cryptography and it summarized the research status of multi-user quantum key distribution.It summarized the quantum key distribution technology which involved the foundation of physics,the protocols of quantum key distribution and the principle of quantum key distribution system.The basic of theory laid a foundation for the study.The polarization insensitive phase modulation system was proposed in this paper.It was based on the instruments of polarization sensitive and modulated the phase twice.It was used for "plug&play"quantum key distribution system.It is a simple and robust way.It can compensate the phase jitter and birefrigent effect at the same time.The visibility can be 96.96%and it can stay stable for a long time.A scheme of multi-user network for quantum key distribution was also proposed.It accomplished Alice communicated with many Bobs and the users could be increase along with adding the amount of the wavelength division multiplexing.The system is simple and easy to operate.It realized wavelength division multiplexing and time division multiplexing at the same time.We use a phase encoding and polarization measurement way to verify the system.It can get a high visibility and keep stable for a long time. |
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