Ideal randomness is one of most important conditions for the implementation of continuous-variable quantum key distribution (CVQKD). However, imperfect randomness may exist in a practical CVQKD system due to imperfections in Gaussian modulation or in random-number generators. Here we propose a weak randomness attack model in practical CVQKD systems to investigate the practical performance of the systems with imperfect randomness, where the prepared coherent states based on nonrandom state modulation are assumed to be known by Eve. Then, we perform parameter estimation and calculate the secret key rate of the system based on the proposed attack model. The simulation results demonstrate that a small imperfect randomness can dramatically reduce the secret key rate of the system, which may seriously limit the practical performance of the system. Therefore, true random numbers and perfect Gaussian modulation are key for practical CVQKD systems.

中文翻译：

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具有弱随机性的实用连续变量量子密钥分发系统的性能分析

理想随机性是实现连续变量量子密钥分配（CVQKD）的最重要条件之一。但是，由于高斯调制或随机数发生器的不完善，实际的CVQKD系统中可能存在不完善的随机性。在这里，我们提出了一个在实际CVQKD系统中的弱随机性攻击模型，以研究具有不完全随机性的系统的实际性能，其中假定基于非随机状态调制而准备的相干态被Eve所知。然后，我们基于提出的攻击模型执行参数估计并计算系统的秘密密钥率。仿真结果表明，不完善的随机性会大大降低系统的秘密密钥率，这可能严重限制系统的实际性能。