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<p>Twin-field quantum key distribution elevates the secure key rate from a linear to a square-root dependence on channel loss and preserves the measurement-device-independent security. This protocol is uniquely positioned to enable global-scale quantum networks, even under extreme channel loss. Although fibre-based twin-field quantum key distribution implementations have advanced rapidly since its proposal, free-space realizations have remained elusive due to atmospheric-turbulence-induced phase distortions. Here we report an experimental demonstration of free-space twin-field quantum key distribution over 14.2-km urban atmospheric channels, surpassing the effective atmospheric thickness—a critical threshold for satellite compatibility. We achieve a secret key rate exceeding the repeaterless capacity bound, a milestone for practical quantum communication. Our approach eliminates the need for an auxiliary channel to stabilize a closed interferometer, instead leveraging open-channel time and phase control of optical pulses. This work represents a pivotal advance towards satellite-based global quantum networks, combining high-speed key distribution with inherent resistance to real-world channel fluctuations.</p>

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Free-space twin-field quantum key distribution

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Yu-Huai Li,
  • Ting Zeng,
  • Min-Yan Wang,
  • Cong Jiang,
  • Jin Lin,
  • Hao-Bin Fu,
  • Xin-Yang Zheng,
  • Jiu-Peng Chen,
  • Zeng-Sen Lin,
  • Cheng-Lin Li,
  • Jian-Yu Guan,
  • Yang Li,
  • Qi Shen,
  • Hao Li,
  • Lixing You,
  • Zhen Wang,
  • Fei Zhou,
  • Juan Yin,
  • Sheng-Kai Liao,
  • Ji-Gang Ren,
  • Xiang-Bin Wang,
  • Yuan Cao,
  • Qiang Zhang,
  • Cheng-Zhi Peng,
  • Jian-Wei Pan

摘要

Twin-field quantum key distribution elevates the secure key rate from a linear to a square-root dependence on channel loss and preserves the measurement-device-independent security. This protocol is uniquely positioned to enable global-scale quantum networks, even under extreme channel loss. Although fibre-based twin-field quantum key distribution implementations have advanced rapidly since its proposal, free-space realizations have remained elusive due to atmospheric-turbulence-induced phase distortions. Here we report an experimental demonstration of free-space twin-field quantum key distribution over 14.2-km urban atmospheric channels, surpassing the effective atmospheric thickness—a critical threshold for satellite compatibility. We achieve a secret key rate exceeding the repeaterless capacity bound, a milestone for practical quantum communication. Our approach eliminates the need for an auxiliary channel to stabilize a closed interferometer, instead leveraging open-channel time and phase control of optical pulses. This work represents a pivotal advance towards satellite-based global quantum networks, combining high-speed key distribution with inherent resistance to real-world channel fluctuations.