Study On High Efficient And Long-distance Measurement Device Independent Quantum Key Distribution

Measurement-device-independent quantum key distribution(MDI-QKD) protocol could remove the security loopholes caused by measurement device in the quantum key distribution protocol, and double the communication distance. However, higher key generation rate and longer distance MDI-QKD protocol are the trends for QKD. The thesis proposes a high efficient MDI-QKD protocol by combining the pulse position modulation(PPM) technology with MDI-QKD protocol. At the same time, quantum memories are used to realize the function of quantum repeaters in MDI-QKD protocol to obtain long distance.The main results are the following:(1) The thesis proposes a MDI-QKD protocol based on PPM modulation, named PPM-MDI-QKD. The new protocol combines PPM with MDI-QKD. In the protocol, Alice and Bob successively encode their weak pulses with polarization encoding, PPM mudulation and decoy state modulation separately, and send the quantum states to a third party Charlie. Alice and Bob could extract the security key after the announcement of the measurement results by Charlie. The deduction of the key generation rate is presented, and the simulation results show that the key generation rate of the PPM-MDI-QKD protocol is improved in comparison with that of the conventional MDI-QKD protocol.(2) Moreover, the thesis gives a high efficient PPM-MDI-QKD protocol using orbital angular momentum(OAM), named PPM-OAM-MDI-QKD. The detailed description of the protocol is presented, and the formula to derive the key generation rate is given. The simulation results show that the key generation rate of PPM-OAM-MDI-QKD protocol is improved. Meanwhile, the proposed protocol has a better performance in comparision with the PPM-MDI-QKD protocol, because OAM encoding is a basis-independent encoding.(3) Furthermore, the thesis gives a long-distance OAM-MDI-QKD protocol based quantum memory. Quantum memories are used to realize the function of quantum repeaters in the conventional OAM-MDI-QKD protocol. This can effectively extend the communication distance of QKD. The detailed description and theoretical derivation of the proposed protocol are presented, and the simulation results show that the key generation rate of long-distance OAM-MDI-QKD protocol is better than that of the conventional OAM-MDI-QKD protocol. The key security transmission distance of the OAM-MDI-QKD protocol could extend to more than 500 km, which is at least 175 km longer than that of the conventional OAM-MDI-QKD protocol.