Research On Implementation And Parameters Optimization Of Plug-and-play RFI-MDI-QKD System

Quantum Key Distribution is based on the basic physical principles in quantum mechanics to ensure unconditional security during key distribution.However,in the actual implementation process of the quantum key distribution protocol,because the performance of the actual device is not enough to meet the theoretical assumptions,it leaves many security holes.Fortunately,for these security vulnerabilities,people have improved the QKD system through the improved QKD protocol,such as the MDI-QKD(Measurement-DeviceIndependent Quantum Key Distribution,MDI-QKD)protocol.It can be immune to all attacks against the measurement unit equipment.In addition,combined with decoy technology,the security of the source of the system can also be guaranteed.However,since the MDI-QKD system needs to align the polarization and phase reference frames in the specific implementation process,additional equipment is needed to increase the complexit y of the system.The plug-and-play RFI-MDI-QKD(Reference-Frame-Independent and Measurement-Device-Independent Quantum Key Distribution,RFI-MDI-QKD)protocol,by combining the RFI-MDI-QKD protocol and the MDI-QKD protocol of untrusted sources,makes the system is not only immune to all attacks on the measurement end,but also makes the system not need to align the reference frame,and only uses one light source on the measurement unit,which greatly reduces the implementation complexity.Based on this,this article mainly studies the parameters optimization and the design and implementation of the system coding unit of the plug-and-play RFI-MDI-QKD protocol.First,the basic concepts of quantum key distribution are briefly introduced,and the theoretical and experimental research progress and future development prospects of quantum key distribution are given.Secondly,the basic knowledge of quantum mechanics and quantum optics related to the distribution of quantum keys and the QKD system of plug-and-play structure are introduced;the background and basic principles of the decoy state protocol are introduced,which lays the foundation for the parameter optimization in the following;emphasized the basic principles of the plug-and-play RFI-MDI-QKD protocol and the key rate calculation method.Third,parameters optimization is performed for the plug-and-play RFI-MDI-QKD system,including partial optimization and full optimization,and the comparison of the optimiza t io n results at different phase angles of reference frames and different transmission distances.The results show that under shot distance,the key rate of the partially optimized result is slightly higher than the key rate of the original literature of the plug-and-play RFI-MDIQKD system,and the ful y optimized key rate is an order of magnitude higher than that of the original literature.At long distances,it is found that the decoy state parameters of the original literature are just the local optimal values of partial optimization and full optimization.Under the different relative angle of the reference system with the same transmission distance,part optimization results show that as the relative phase angle increases,the key rate of the system decreases,while under the different relative angle of the reference system,full optimization results shows that the key rate of the QKD system is basically the same.Fourth,the coding unit of the plug-and-play RFI-MDI-QKD system is designed and implemented.It is mainly divided into three modules:(1)PC and FPGA communica t io n module,which is mainly responsible for generating random numbers in the PC,and then the random number is sent to the FPGA through the PCI-e interface between the PC and the FPGA,and the DC-FIFO is used to cache the random number in the FPGA;(2)The encoding and output module in FPGA reads the random number in DC-FIFO,and then generates and outputs the digital signal that controls the intensity modulator and phase modulator according to the requirements of time-bin phase encoding and the decoy state parameters obtained after full optimization.(3)The amplitude control module,it is used to receive the digital control signals for controlling the intensity modulator and phase modulator,and then adjust the amplitude of the digital signal through radio frequency amplifier,DAC,etc.,and then send it to the electro-optic modulator.Fifth,summarize the full text and look forward to future work.