Reem Mandil

Twin-field quantum key distribution (TFQKD) systems have shown great promise for implementing practical long-distance secure quantum communication due to its measurement-device-independent nature and its ability to offer fundamentally superior rate-loss scaling than conventional point-to-point QKD systems. A surge of research has produced many variants of protocols and experimental demonstrations. To make TFQKD more applicable in quantum communication, a study of TFQKD in a networking setting is essential. In this work, we experimentally demonstrate a proof-of-principle Sagnac-interferometer based TFQKD network with three users and one untrusted central node. We show that our network enables users to share secure keys with channel losses up to 58dB, and channel loss asymmetric up to 15dB. In some cases, the secure key rates still beat the rate-loss bounds for conventional point-to-point repeaterless QKD systems. It is to our knowledge the first multi-user-pair TFQKD network demonstration, an important step in advancing quantum communication network technologies.