| Information security is a research field with important strategic significance and practical value related to national and personal information security.With the improvement of computer computing power,especially the rapid development of quantum computing,the original classical cryptosystem(especially public key cryptography)faces the risk of being deciphered.Therefore,it is urgent to study a cryptographic system that can withstand quantum computing.Quantum key distribution is based on the basic principles of quantum physics and has theoretical unconditional security.Among them,the continuous variable quantum key distribution system has been widely studied.The paper firstly sorts out the development status of continuous variable quantum key distribution at home and abroad.Then the basic theory is expounded,and the source and form of excess noise in the continuous variable quantum key distribution system based on coherent state protocol is analyzed.Finally,focusing on two types of excess noise,which have a great impact on system performance,modulation excess noise and phase compensation excess noise,modeling analysis and suppression methods are studied from both theoretical and experimental aspects.The main content of the paper are as follows:1.A high-precision and high-stability amplitude modulation scheme based on Sagnac loop is designed and realized.The validity and feasibility of the scheme are verified in the prototype system,which guarantees the development and performance evaluation of the engineering prototype of the continuous variable quantum key distribution system.2.A high-precision phase compensation scheme based on mean denoising is proposed for reducing estimation errors.An experimental scheme of mean denoising suitable for the prototype system is designed.The experimental results show that when the signal-to-noise ratio is 0.22,the scheme can reduce the over-noise of the system to30% to the greatest extent,and effectively improve the performance of the system. |
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