Quantum key distribution over 658 km fiber with distributed vibration sensing

TL;DR

This paper demonstrates a record-breaking 658 km quantum key distribution over ultra-low-loss fiber and utilizes the system's phase information to detect and locate fiber vibrations, enabling applications in secure communication and remote sensing.

Contribution

It achieves the longest secure quantum key distribution distance and introduces vibration sensing using phase information in TF-QKD systems.

Findings

Secure key distribution over 658 km fiber

Vibration perturbation detection with sub-kilometer resolution

Potential applications in earthquake and landslide monitoring

Abstract

Twin-field quantum key distribution (TF-QKD) promises ultra-long secure key distribution which surpasses the rate distance limit and can reduce the number of the trusted nodes in long-haul quantum network. Tremendous efforts have been made towards implementation of TF-QKD, among which, the secure key with finite size analysis can distribute more than 500 km in the lab and in the field. Here, we demonstrate the sending-or-not-sending TF-QKD experimentally, achieving a secure key distribution with finite size analysis over 658 km ultra-low-loss optical fiber, improve the secure distance record by around 100 km. Meanwhile, in a TF-QKD system, any phase fluctuation due to temperature variation and ambient variation during the channel must be recorded and compensated, and all these phase information can then be utilized to sense the channel vibration perturbations. With our QKD system, we recovered the external vibrational perturbations on the fiber generated by an artificial vibroseis and successfully located the perturbation position with a resolution better than 1 km. Our results not only set a new distance record of QKD, but also demonstrate that the redundant information of TF-QKD can be used for remote sensing of the channel vibration, which can find applications in earthquake detection and landslide monitoring besides secure communication.