Experimental Research On Quantum Cryptography

Since ancient times, secret communication plays a unique role in military and diplomacy. Cryptology is one of the technical tools for secret communications, where secrecy is based on the secrecy of keys. Modern cryptology is divided into two parts, private-key system and public-key system. For private-key system, the biggest problem is how to distribute keys safely and effectively. Scientists have worked on it for hundred years, but didn't find a good solution to it. The secrecy of the public-key system has not been proved extensively, because its secrecy is based on computational complexity. However, with the improvement of computer technology and the present of quantum computer, many difficult questions now may be solved easily in future. As a combination of quantum mechanics and cryptology, quantum cryptography solves the above dilemma ingeniously. The secrecy of quantum cryptography is based on principles of quantum mechanics: the non-cloning theorem and the uncertainty principle. As long as principles of quantum mechanics are correct, the secrecy of quantum cryptography can be confirmed. The quantum key distribution can be operated through a public channel without worrying about eavesdropping because any eavesdropping can be intercepted by users. Since the first quantum key distribution protocol was presented by Bennett, this new field has been developed rapidly. Now, quantum cryptography has become a commercial technology and is tested in information area.The main content of this dissertation is the experimental investigation of quantum key distribution. We can draw the outline of this dissertation as follows:1. An experimental setup for quantum key distribution with 850nm single mode fiberwas established. The system is developed based on Mach-Zehnder interferometer, in which the difference of two arms of interferometer is 8 meter. The transmission line is...