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Gbps key rate passive-state-preparation continuous-variable quantum key distribution within access-network area
Photonics Research- received 01/25/2024; accepted 04/22/2024; posted 04/22/2024; Doc. ID 519909
- Abstract: The conventional Gaussian-modulated coherent-state quantum key distribution (QKD) protocol requires the sender to perform active modulations based on 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 access-network area using high-bandwidth detectors with 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 efficient, low noise and high bandwidth. The secure key rate over transmission distances of 5.005 km with and without consideration of finite-size effect are 273.25 Mbps and 1.09 Gbps. The use of PSP method boosts the asymptotic secret key rate of CVQKD to Gbps level for the first time within the range of the access network, which provides an effective and secure key distribution strategy for high-speed quantum cryptography access communication.