Measurement-Device-Independent Twin-Field Quantum Key Distribution (1805.12004v3)

Abstract: The ultimate aim of quantum key distribution (QKD) is improving the performance of transmission distance and key generation speed. Unfortunately, it is believed to be limited by the secret-key capacity of quantum channel without quantum repeater. Recently, a novel twin-field QKD (TFQKD) [Nature 557, 400 (2018)] is proposed to break through the limit, where the key rate is proportional to the square-root of channel transmittance. Here, by using the vacuum and one-photon state as a qubit, we show that the TF-QKD can be regarded as a measurement-device-independent QKD (MDI-QKD) with single-photon Bell state measurement. Therefore, the MDI property of TF-QKD can be understood clearly. Importantly, the universal security proof theories can be directly used for the TF-QKD, such as BB84, six-state and reference-frame-independent schemes. Furthermore, we propose a feasible experimental scheme for the proof-of-principle experimental demonstration.