The conventional Gaussian-modulated coherent-state quantum key distribution (QKD) protocol requires the sender to perform active modulations based on a true random number generator. Compared with it, the passive-state-preparation (PSP) continuous-variable quantum key distribution (CVQKD) equivalently performs modulations passively by exploring the intrinsic field fluctuations of a thermal source, which offers the prospect of chip integration QKD with low cost. In this paper, we propose and experimentally demonstrate a high-rate PSP-CVQKD scheme within an access-network area using high-bandwidth detectors in a continuous wave encoding and decoding way. By proposing effective methods for suppressing the noises during the PSP process and polarization multiplexing to decrease the photon leakage noises, we realize the high-intensity local oscillator transmission, thereby achieving coherent detection with high efficiency, low noise, and high bandwidth. The secure key rates over transmission distance of 5.005 km with and without consideration of the finite-size effect are 273.25 Mbps and 1.09 Gbps. The use of the PSP method boosts the asymptotic secret key rate of CVQKD to Gbps level for the first time, to our knowledge, within the range of the access network, which provides an effective and secure key distribution strategy for high-speed quantum cryptography access communication.

中文翻译：

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接入网络区域内 Gbps 密钥速率被动状态准备连续可变量子密钥分发


传统的高斯调制相干态量子密钥分发（QKD）协议要求发送方基于真随机数生成器执行主动调制。与之相比，被动状态准备（PSP）连续可变量子密钥分配（CVQKD）通过探索热源的本征场涨落，等效地被动地进行调制，为低成本芯片集成QKD提供了前景。在本文中，我们提出并通过实验演示了一种在接入网络区域内使用高带宽检测器以连续波编码和解码方式的高速 PSP-CVQKD 方案。通过提出有效的PSP过程噪声抑制方法和偏振复用降低光子泄漏噪声，实现高强度本振传输，从而实现高效率、低噪声、高带宽的相干检测。在考虑和不考虑有限尺寸效应的情况下，5.005 km传输距离上的安全密钥速率分别为273.25 Mbps和1.09 Gbps。据了解，PSP方法的使用首次在接入网范围内将CVQKD的渐近密钥速率提升至Gbps级别，为高速量子密码接入提供了有效、安全的密钥分发策略沟通。