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arXiv · 2609.04447

Proof-of-principle long-distance Sagnac twin-field quantum key distribution network

Reem Mandil·Yen-An Shih·Abhay Verma·Li Qian·Hoi-Kwong Lo
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Abstract

Twin-field (TF) quantum key distribution (QKD) offers a promising approach to long-distance QKD networks due to its superior performance over large channel losses. Due to specialized hardware requirements, nearly all long-distance TFQKD demonstrations have only two users exchanging keys, rather than a network with three or more users. In this work, we experimentally demonstrate a proof-of-principle three-user-pair Sagnac TFQKD network spanning 127-km using single-photon avalanche detectors without any active phase stabilization or postcompensation. We implement efficient procedures for maintaining polarization stability and circumventing Rayleigh backscattering noise to achieve a stable Sagnac interference visibility of $93\pm1$% over one hour. A secure key rate of $1.398\times10^{-5}$ bits per pulse is achieved over an asymmetric communication channel with 102-km fiber and 45-dB overall loss. To our knowledge, this is the first TFQKD network without active phase stabilization or postcompensation achieved over long fibers. Our results represent a highly practical and cost-effective approach to long-distance QKD networks.

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Reem Mandil, Yen-An Shih, Abhay Verma, Li Qian, Hoi-Kwong Lo. 2026-09-03. Proof-of-principle long-distance Sagnac twin-field quantum key distribution network. https://arxiv.org/abs/2609.04447

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