Study On Quantum Key Distribution In Optical Fiber

In all ages, the security of communication is much accounted of. In 20th century, the century of information, the security of communication has been closely bound up with people's daily life. Many methods have been developed to encrypt information. Whatever method to choose, the basic demand is to make anyone else who gets the encrypted information cannot get the true information.Encrypting systems employed at present usually base the security of communication on the arithmetic complexity. However, this system is confronted with a great challenge because of the rapid development of quantum mechanics. Once magnitude breakthrough comes forth, the mightiness computing capability of quantum computer will make the existing encrypting system invalid. Quantum mechanics bring forward an alternative measure answering to the security crisis of communication invited by itself. That is, build a secure key through quantum key distribution (QKD) and apply it to a "one-time-pad" encrypting system. The absolutely security of the both procedure ensures the security of the communication. Differring from the classic communication, QKD bases the security on the foundational physics principles and any attempt to eavesdrop any information illegally will be discovered. Since the first QKD protocol being put forward, researches in this field grew rapidly.This article is written on this topic and it has several objectives.Firstly, after chiefly presenting the classic cryptography, we particularly explain the prevalent protocols for QKD. Then the security and efficiency of the rotocols are simply commpared and contrasted. We review the researches being carried out at domestic and abroad, within which we put emphasis on the researches on experiments.Secondly we contrast the characteristic of the two main ways used in QKD system. And the existing experimental systems employing phase coding for QKD in optical fiber are narrated.Then a new protocol for QKD in optical fiber under collective-noise is put forward. The protocol employs the singled state as the information carrier, taking advantage of its property that it is invariable under equal rotations on both qubits.Finally the experimental system which we set up is particularly presented. We discuss the results we get and analyze the error. Aiming at improve our system, we advance some notions for ameliorating. For the sake of putting our system into utility, we have many things to do to enhance the system.