Quantum Key Distribution over 658 km Fiber with Distributed Vibration Sensing.

Area of Science:

• Quantum Information Science
• Optical Communications
• Sensing Technology

Background:

• Twin-field quantum key distribution (TFQKD) offers extended secure communication ranges beyond traditional limits.
• Existing TFQKD systems have demonstrated secure key distribution over 500 km.
• Phase fluctuations in quantum channels can be a source of noise but also contain valuable environmental information.

Purpose of the Study:

• To experimentally demonstrate a new distance record for TFQKD.
• To explore the use of TFQKD phase information for remote sensing of channel vibrations.
• To assess the feasibility of TFQKD for applications beyond secure communication.

Main Methods:

• Implementation of a sending-or-not-sending TFQKD protocol.
• Utilizing phase fluctuation data from the quantum channel for vibration sensing.
• Conducting experiments with artificial vibrations to test sensing capabilities over a 658 km fiber link.

Main Results:

• Achieved secure key distribution over a 658 km ultra-low-loss optical fiber, setting a new distance record.
• Successfully recovered and located external vibrational perturbations with a resolution better than 1 km.
• Demonstrated the dual capability of TFQKD for secure communication and environmental sensing.

Conclusions:

• TFQKD can establish secure communication links over unprecedented distances.
• Phase information within TFQKD systems can be leveraged for high-resolution remote sensing of channel vibrations.
• This technology has potential applications in areas such as earthquake monitoring and landslide detection, in addition to secure communications.