Research On Key Technology In Continuous Variable Quantum Key Distribution

Quantum cryptography, based on cryptography and quantum mechanics, using the method of physics, because of its security and the detection of eavesdropping, have good safety performance and application prospect. Continuous variables quantum cryptography using Gaussian state (coherent states and squeezed state) as the carrier, modulate the light pulses in amplitude and phase at the sender and measure with homodyne detection at the receiver. The use of Continuous variable quantum system has some potential advantages over single-photon quantum system. Such advantages lie in the prospect for higher optical data rates and simpler processing tools, based upon standard telecommunication techniques. Therefore, theoretic and experimental research on continuous variables quantum cryptography is of great significance.Our research team dedicated to continuous variable quantum cryptography theory research and technology implementation, and has developed continuous variables quantum key distribution system preliminarily. This paper discussed some of the key technology in continuous variable quantum key distribution:1) The generation of Gaussian source is one of the key elements in continuous-variable quantum communication, especially in continuous-variable quantum cryptography communication, which is closely associated with the core problems of a communication system, such as efficiency and security, etc. Using Shannon's information-theory model, we studied Gaussian source's effect to channel capacity and security of quantum cryptography communication, we then gave these parameters'dependence on Gaussian source's parameters and the security condition of quantum cryptography communication. Based on all those theoretical analysis, we proposed an experimental method to implement Gaussian-modulation, and used FPGA to generate Gaussian source experimentally.2) Phase modulator and amplitude modulator are both indispensable optical modulator in continuous variables quantum key distribution. In this paper, we proposed a design of drive module and a performance monitoring system for LiNbO3 phase modulator and amplitude modulator. The feasibility and reliability of the scheme are verified through the experimental result and theoretical analysis.