Mode-pairing quantum key distribution

• Published in: Nature communications Vol. 13; no. 1; p. 3903
• Main Authors: Zeng, Pei, Zhou, Hongyi, Wu, Weijie, Ma, Xiongfeng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.07.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/400/482; 639/766/483/481; Communication; Frequency dependence; Humanities and Social Sciences; Interference; Interferometers; Locking; multidisciplinary; Photons; Quantum cryptography; Quantum theory; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-31534-7

Quantum key distribution — the establishment of information-theoretically secure keys based on quantum physics — is mainly limited by its practical performance, which is characterised by the dependence of the key rate on the channel transmittance R ( η ). Recently, schemes based on single-photon interference have been proposed to improve the key rate to R = O ( η ) by overcoming the point-to-point secret key capacity bound with interferometers. Unfortunately, all of these schemes require challenging global phase locking to realise a stable long-arm single-photon interferometer with a precision of approximately 100 nm over fibres that are hundreds of kilometres long. Aiming to address this problem, we propose a mode-pairing measurement-device-independent quantum key distribution scheme in which the encoded key bits and bases are determined during data post-processing. Using conventional second-order interference, this scheme can achieve a key rate of R = O ( η ) without global phase locking when the local phase fluctuation is mild. We expect this high-performance scheme to be ready-to-implement with off-the-shelf optical devices. Measurement-device-independent QKD schemes suffer from a trade-off between ease of implementation (avoiding the need for global phase locking) and high rates (quadratic improvement in rate). Here, the authors propose a protocol which offers both simple implementation and strong performances.