Hardware Implementation Technology Study Of High-speed Continuous Variable Quantum Key Distribution System

Quantum key distribution(QKD),as an important research subject in the field of quantum cryptography and quantum information processing,enables two correspondents to share a secret key.It's unconditional security is guaranteed by the fundamental principles of quantum mechanics.As an important branch of QKD,continuous variable quantum key distribution(CV-QKD)has shown its potential advantages in secret key rate,detection efficiency,device compatibility etc.,and received extensive attention from the researchers at home and abroad in recent years.Currently,Gaussian-modulated coherent state(GMCS)CV-QKD is a research hotspot.The unconditional security of GMCS CV-QKD protocols have been fully proved.Moreover,great progresses have been achieved in experiment,i.e.,long secure distance and high speed GMCS CV-QKD have been experimentally demonstrated by using commercial components.However,there are still many problems to be solved in current CV-QKD systems,such as poor stability,low efficiency,low secret key rate,poor integration,non-ideal practical security etc.And system hardware is one of the main causes of these problems.Therefore,from the perspectives of system hardware design and implementation,we can effectively solve the above problems and then provide technical support for the practical application of CV-QKD.In this dissertation,we focus on how to improve the performance and practical security of high-speed CV-QKD system based on hardware design and implementation.The main innovative results are listed as follows:1.Practical security of the finite sampling bandwidth effects in high-speed CV-QKD system is analyzed and studied.We analyze the origin of the finite sampling bandwidth effects,that is,finite sampling bandwidth of the employed analog-to-digital converter at the receive's side leads to inaccurate results of pulse peak sampling.Then,errors are introduced in parameter estimation and secret key rate calculation processes.And security loopholes are exposed to eavesdroppers as a result.In order to solve these problems,we propose a high-precision data acquisition scheme,and demonstrate the effectiveness of the new proposed scheme in removing the finite sampling bandwidth effects.Moreover,we give a brief discussion about hardware implementation of the new scheme in practical CV-QKD system.The results show that the new proposed scheme can fully remove the finite sampling bandwidth effects,and helps to resist some attacks in practical CV-QKD system and improve practical security.What's more,this new scheme is easy to implement and cost less,which provides a useful reference for improving the performance of high-speed CV-QKD system.2.Design and implementation of FPGA-based frame synchronization and phase compensation algorithms in CV-QKD system are discussed.We analyze the difficulties in designing high performance frame synchronization module and phase compensation module,and give a brief introduction of the exsited solutions.Then two FPGA-based algorithms,i.e.,frame synchronization algorithm and phase drift estimation algorithm are proposed.Moreover,these two new algorithms are analyzed and verified in performance,complexity and resource consumption.This work provides support to achieve a more-stable,better-performance,higher-integration CV-QKD system.