Experimental demonstration of quantum downstream access network in continuous variable quantum key distribution with a local local oscillator

• Dengke Qi, Xiangyu Wang, Zhenghua Li, Jiayu Ma, Ziyang Chen, Yueming Lu, and Song Yu
• received 01/16/2024; accepted 04/04/2024; posted 04/04/2024; Doc. ID 519140
• Abstract: Quantum networks provide opportunities and challenges across a range of intellectual and technical frontiers, including quantum computation, communication and others. Unlike traditional communication networks, quantum networks utilize quantum bits rather than classical bits to store and transmit information. Quantum key distribution (QKD) relying on the principles of quantum mechanics is a key component in quantum networks enables two parties to produce a shared random secret key, thereby ensuring the security of data transmission. In this work, we propose a cost-effective quantum downstream access network structure in which each user can get their corresponding key information through terminal distribution. Based on this structure, we demonstrate the first four-end-users quantum downstream access network in continuous variable QKD with a local local oscillator. In contrast to point-to-point continuous variable QKD, the network architecture reevaluates the security of each user and accounts for it accordingly, and each user has a lower tolerance for excess noise as the overall network expands with more users. Hence, the feasibility of the experiment is based on the analysis of theoretical model, noise analysis, and multiple techniques such as particle filtering and adaptive equalization algorithm used to suppress excess noise. The results show that each user can get a low level of excess noise and can achieve secret key rate of 546 kbps, 535 kbps, 522.5 kbps and 512.5 kbps under transmission distance of 10 km, respectively with the finite-size block of 1×10⁸. This not only verifies the good performance but also provides the foundation for the future multi-users quantum downstream access network.