Quantum key distribution over a 2 km free-space channel with a high secure key rate

@misc{park2026quantum,
  title = {{Quantum key distribution over a 2 km free-space channel with a high secure key rate}},
  author = {Kyungdeuk Park and Dongkyu Kim and Dong-Gil Im and Yonggi Jo and Jisu Kim and Jonguk Choi and Yong Sup Ihn},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2607.24118},
  eprint = {2607.24118},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.24118},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Quantum key distribution over a 2 km free-space channel with a high secure key rate
AU  - Kyungdeuk Park
AU  - Dongkyu Kim
AU  - Dong-Gil Im
AU  - Yonggi Jo
AU  - Jisu Kim
AU  - Jonguk Choi
AU  - Yong Sup Ihn
PY  - 2026
DA  - 2026/10/16
PB  - arXiv
DO  - 10.48550/arxiv.2607.24118
UR  - https://arxiv.org/abs/2607.24118
AB  - Free-space quantum key distribution (QKD) provides crucial advantages, including mobility and deployment exibility, for securing next-generation communication networks. However, atmospheric turbulence and beam wander severely degrade single-photon coupling effciency and link stability over outdoor channels. In this work, we experimentally demonstrate a free-space decoy-state BB84 QKD system operating at 803 nm with a 100 MHz repetition rate over a 2 km outdoor link. By employing an active beam-wander correction based on fast-steering mirrors (FSMs) and position sensitive detectors (PSDs) with a 500 Hz control loop, we enhance the ?ber coupling effciency and achieve an average ?nite-key secure key rate of 110 kbps with an average quantum bit error rate (QBER) of 3.28 %, representing a 2.5 times secure key rate enhancement under an active beam stabilization. This work demonstrates the indispensability of active beam stabilization and provides an operational reference for robust, long-range free-space quantum communication.
ER  -