In previous continuous-variable quantum key distribution (CV-QKD) systems, the transmission rate is limited by the Nyquist criterion. Since the data symbols transmit without intersymbol interference (ISI) under this limitation, how to improve the secret key rate is still a notoriously hard problem. Faster-than-Nyquist (FTN) technology has been viewed as a potential technique in future communication systems, because of its higher spectrum efficiency and faster symbol rate. In this paper, a CV-QKD system based on FTN is proposed. The transmission of an FTN system is simulated, and then we analyze the Mazo limit and the constrained capacities of the system, and finally compare the secret key rate of FTN signals and Nyquist signals. Our proposed scheme is especially beneficial for the high-speed scenario. Simulation results demonstrate that such a CV-QKD system can increase channel capacity and enhance key rate; it can also improve the safe transmission distance of CV-QKD.

中文翻译：

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基于比奈奎斯特算法更快的连续变量量子密钥分配

在以前的连续变量量子密钥分配（CV-QKD）系统中，传输速率受奈奎斯特准则的限制。由于在此限制下数据符号的传输没有符号间干扰（ISI），因此如何提高秘密密钥速率仍然是一个众所周知的难题。快于奈奎斯特（FTN）技术由于其更高的频谱效率和更快的符号速率而被视为未来通信系统中的一种潜在技术。本文提出了一种基于FTN的CV-QKD系统。模拟了FTN系统的传输，然后分析了Mazo限制和系统的受约束能力，最后比较了FTN信号和奈奎斯特信号的秘密密钥率。我们提出的方案对于高速场景特别有益。仿真结果表明，这种CV-QKD系统可以增加信道容量并提高密钥速率。它还可以提高CV-QKD的安全传输距离。