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Implementation of a twin-field quantum key distribution network faces limitations, including the low tolerance of interference errors for phase-matching-type protocols and the strict constraint regarding intensity and probability for sending-or-not-sending-type protocols. Here we propose a two-photon twin-field quantum key distribution protocol and achieve twin-field-type two-photon interference through postmatching phase-correlated single-photon interference events. We exploit the noninterference mode as the code mode to highly tolerate interference errors and the two-photon interference naturally removes the intensity and probability constraint. Therefore, our protocol can transcend the above-mentioned limitations while breaking the secret key capacity of repeaterless quantum key distribution. Simulations show that for a four-user network, under which each node with fixed system parameters can dynamically switch different attenuation links, the key rates of our protocol for all six links can either exceed or approach the secret key capacity. However, the key rates of all links are lower than the key capacity when using phase-matching-type protocols. Additionally, four of the links could not extract the key when using sending-or-not-sending-type protocols. We anticipate that our protocol can facilitate the development of practical and efficient quantum networks.
Xie et al. (Fri,) studied this question.