The Research Of Quantum Communication Based On Orbital Angular Momentum State Of Photon

With the advent of the information age, computer and Internet technology have a rapid development. Meanwhile,mobile phone and other mobile communication terminals become more and more popular in public,promoting the progress of the mobile network technology. Consequently,the contradictions between the requirement of larger channel capacity and the shortage of spectrum resource are highlighted. Moreover, there has been a growing interest in communication security as it's closely bound up to everyone's daily life. To address this difficulty, some useful methods and technologies had been put forward by scientists, such as dense wavelength division multiplexing, mode division multiplexing, etc.Although these technologies have a certain extent alleviated the problem of shortage of spectrum resource, the limited channel capacity can often be a serious handicap to the development of information and communications technology.Orbital angular momentum is the physical quantity of describing the helical wave fronts of optical vortex beams and optical vortices. Since the optical vortex beam has a new degree of freedom namely orbital angular momentum, which can be used as a new kind of information carrier to largen the capability of channels without adding bandwidth. In this article,we present an study of higher-dimensional quantum secret sharing protocols based on mutually unbiased bases, implemented by means of photons carrying orbital angular momentum, which is the main contents of this paper. The main contents of this paper are as follows.Firstly we took the famous quantum key distribution protocol, BB84 protocol, for example to introduce some quantum physics and information theories. Besides, an improved safety analysis based on this protocol is also presented in this paper. And then a scheme of circular quantum secret sharing by using polarization encoding and single photon detector as we became familiar with BB84 protocol. In this circular quantum secret sharing protocol,the four polarization states of photons are used to pass on information and encoded by two unitary operations, which made the protocol more secure. What's more, we had completed an safety analysis to prevent the attack of eavesdropper, such as intercept-resend attack.Secondly we introduced the basic theory of orbital angular momentum of optical vortex beams as well as the preparation methods and measuring methods of orbital angular momentum, and then combine the theory of orbital angular momentum of optical vortex beams to the protocol of circular quantum secret sharing, creating a new scheme of quantum secret sharing which is in higher dimension. The physical implementation of the protocol, including measurement module and encoding module.Finally we analyze and evaluate the security of this protocol, showing that it can resist the general attack of eavesdropper, such as intercept-resend attack.