Analysis And Calculation Of Practical Security Of New Quantum Key Distribution Protocols

The security of traditional cryptography is realized based on the complexity of the algorithm,thus the security of the keys can be guaranteed just within a certain period of time.With the development of new deciphering algorithms and the study of quantum computers,traditional cryptographic systems is bound to be no longer safe.In response to the above problems,quantum secret communication has emerged.Its security relies on the principle of quantum physics,rather than the complexity of solving mathematical problems.In theory,more computing resources can not effectively help eavesdroppers to crack keys,thus the quantum secret communication has theoretical unconditional security.Quantum secret communication is one of the most direct and mature applications of quantum mechanics in the field of communication.It has always been a hot issue in international research.First of all,this paper will present the research background,research purpose and some latest developments of quantum secret communication at home and abroad.Then some basic knowledge of quantum secret communication is introduced,followed by the introduction of the practicle quantum key distribution protocol.Here,the BB84 protocol and the measurement-device-independent quantum key distribution protocol are mainly described.The BB84 protocol is the earliest proposed quantum key distribution protocol and theoretically has unconditional security.The measurementdevice-independent quantum key distribution protocol can not only resist the attack on the detector side,but also obtain a long transmission distance.In recent years,great progress has been made in both theory and experiment.However,these protocols also have some other problems in practical applications,such as low key rate,short secure transmission distance,and the finite-key-size effect.This paper mainly aims at these deficiencies to propose the corresponding scheme to make up for these defects.It is mainly summarized as the following three aspects:1.In the traditional decoy-state BB84 protocol,both the signal state and the decoy state are prepared under the X-and Z-bases.In our proposed biased-basis scheme,the signal state is prepared under the X and Z bases,while the decoy state is only prepared under the X base.This scheme can not only reduce the number of preparation states at the transmitting side but also reduce the consumption of random numbers.Moreover,it can be seen from the simulation results that the key generation rate and the secure transmission distance can be significantly enhacnced compared with the standard decoy-state BB84 protocol.2.The measurement-device-independent quantum key distribution protocol can obtain a longer transmission distance,but the key rate is not high and the finite-key-size effect cannot be ignored in practical applications.In response to this shortcoming,we applied the latest statistical fluctuation analysis method to the measurement-device-independent quantum key distribution protocol for the first time in combination with the four-intensity method.This scheme not only improves the key generation rate but also has a higher security compared with using the Gaussian approximation method.3.Since there is no ideal single photon source,weak coherent sources and heralded single photon sources are often used instead,but these two sources also have some defects.In response to this,we studied the heralded pair-coherent source and applied it to the latest four-intensity decoy-state measurement-device-independent protocol.The simulation results show that this scheme can greatly improve the key generation rate and transmission distance,and provide a valuable reference for the measurement-device-independent quantum key distribution protocol.