Twin-field (TF) quantum key distribution (QKD) fundamentally alters the rate-distance relationship of QKD, offering the scaling of a single-node quantum repeater. Although recent experiments have demonstrated the new opportunities for secure long-distance communications allowed by TF-QKD, formidable challenges remain to unlock its true potential. Previous demonstrations have required intense stabilization signals at the same wavelength as the quantum signals, thereby unavoidably generating Rayleigh scattering noise that limits the distance and bit rate. Here, we introduce a dual-band stabilization scheme that overcomes past limitations and can be adapted to other phase-sensitive single-photon applications. Using two different optical wavelengths multiplexed together for channel stabilization and protocol encoding, we develop a setup that provides repeater-like key rates over communication distances of 555 km and 605 km in the finite-size and asymptotic regimes respectively and increases the secure key rate at long distance by two orders of magnitude to values of practical relevance.
Bibliographical noteFunding Information:
We thank X.-B. Wang and H. Xu for their useful feedback on the TWCC protocol. We acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under the grant agreement number 857156 ‘OPENQKD’ and under the Marie Skłodowska-Curie grant agreement number 675662. M.M. acknowledges financial support from the Engineering and Physical Sciences Research Council (EPSRC) and Toshiba Europe Limited.
© 2021, The Author(s), under exclusive licence to Springer Nature Limited.
This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details