Research On Sending Or Not Sending Quantum Key Distributebution Protocol

Based on the quantum mechanics,quantum communication is able to guarantee the unconditionally security for the authorized users.Currently,quantum communication is refered to quantum key distribution(QKD)process.The sending-or-not-sending quantum key distribution(SNS-QKD)protocol's is proposed under the inspiration of twin-field quantum key distribution(TFQKD).Like the typical two-way QKD protocol,such as Measurement Device Independent quantum key distribution(MDI-QKD),SNS-QKD is immune to any attack in the detection.Similar to TFQKD,SNS-QKD also can break the limit of secret key capacity(SKC)in absence of quantum repeaters.In addition,SNS-QKD can tolerate the large misalignment errors.Therefore,it becomes a hot topic in the research field of QKD.We study the SNS-QKD protocol in terms of the information source and the information channel.The main works are listed as the following.(1)In order to improve the performance of SNS-QKD,a SNS-QKD protocol based on heralded pair-coherent source(HPCS)is proposed,named HPCS-SNS-QKD.In the comparison with the weak coherent source(WCS),HPCS has lower ratio of vacuum state pulse.Hence the single photon error rate can be effectively reduced in HPCS-SNS-QKD.The relationship between key generation rate and secure transmission distance is derived,and the expression of the key rate under the limited pulses is given.The numerical simulation results show that the proposed HPCS-SNS-QKD can exceed the limit secure distance for single particle QKD,compared with WCS-SNS-QKD,HPCS-SNS-QKD has a longer transmission distance,higher key rate and can endure more misalignment error.For limited pulses in practical experiment,HPCS-SNS-QKD always has a higher key generation rate.(2)In order to implement the SNS-QKD protocol in free space,we propose a SNS-QKD protocol based on the Prefixed-threshold real-time selection.When Alice and Bob send the signal pulses to the intermediate part Charlie,the two channels are not symmetric due to the influenece of the atmospheric turbulence,that will greatly reduce the key generation rate of SNS-QKD protocol.In the proposed SNS-QKD protocol,Charlie prefixes a channel transmittance threshold according to the system's experimental parameters,instead of setting the optimal threshold based on all the data after the communications.The simulation results show that the SNS-QKD based on the prefixed-threshold real-time selection can mitigate the infulence of atmospheric turbulence on SNS-QKD protocol.The SNS-QKD based on the prefixed-threshold real-time selection has a better performance and a longer transmission distance than that one without prefixed-threshold real-time selection.