Reaserch On Quantum Key Distribution Protocol Scheme Based On Phonton Orbital Angular Momentum

Quantum key distribution(QKD) has been proved strictly unconditionally security. However, there are many loopholes in the pratical QKD scheme. Recently developed measurement-device-independent quantum key distribution protocol(MDI-QKD) could solve the security loophole at detectors. On the other hand, orbital angular momentum(OAM) is a new information carrier, which has infinite eignvalues and the orthogonality property among different OAM modes, is applied to QKD scheme. This thesis mainly studies the high dimensional QKD scheme and MDI-QKD scheme based on the orbital angular momentum state.The main works are as follows:(1) Based on BB84 protocol, two high demensional QKD schemes using OAM states(OAM-MDI-QKD) with active decoy states and passive decoy states are proposed. The theoretical analysis for both schemes are presented, and the simulations are given with MATLAB. The simulation result shows that the key generation rate of the proposed high dimensional QKD schemes are improved, and the security are enhanced. Then, the two cases of the high dimention quantum key distribution based on OAM are compared and theoretically simulated. The simulation result shows that, compared with the active decoy state method, the security of the high demensional QKD scheme with the passive decoy state is higher, but the key rate is decreased.(2) Wavelenth Division Mutiplexing(WDM) technology can improve the transmission rate of communication systems. An OAM-MDI-QKD scheme with WDM technique is given. The result shows that WDM technology can improve the key rate of the scheme greatly. On the other hand, an OAM-MDI-QKD with asymmetrical channel transmission efficiency is given. The simulation results show that, asymmetry of channel transmission efficiency reduces OAM-MDI-QKD scheme’s key rate and transmission distance. Studies have show that, the key rate of asymmetrical channel transmission efficiency MDI-QKD scheme can be improved by adjusting the signal intensity. When the ratio of the asymmetrical channel transmission diatance is 0.8, the tolerated channel loss is improved and the key rate of long-distance transmission is enhanced wtih 2μ =0.3 than 2μ =0.5.