An integrated space-to-ground quantum communication network over 4,600 kilometres.

Area of Science:

• Quantum communication
• Network security
• Applied physics

Background:

• Quantum key distribution (QKD) offers secure communication but faces challenges in scaling to global networks.
• Existing QKD networks are limited in range and user distribution.
• Quantum repeaters, a potential solution for global networks, are not yet technologically feasible.

Purpose of the Study:

• To demonstrate an integrated space-to-ground quantum communication network.
• To overcome the limitations of current QKD networks for widespread, secure communication.
• To establish a practical and reliable QKD network infrastructure.

Main Methods:

• Integration of a large-scale fiber QKD network (>2,000 km) with high-speed satellite-to-ground free-space QKD links.
• Utilization of a trusted relay structure for the fiber network to ensure practical security and reliability.
• Deployment of advanced satellite-to-ground QKD for high secret-key rates and reduced channel loss.

Main Results:

• Demonstration of a 4,600 km integrated QKD network, connecting remote users.
• Achieved an average satellite-to-ground secret-key rate of 47.8 kbps, over 40 times higher than previous records.
• Established a fiber network covering over 2,000 km with long-term stability and practical security.

Conclusions:

• The integrated space-to-ground QKD network provides a viable solution for global secure communication.
• The demonstrated technology enables versatile and ultralong quantum links, paving the way for geosynchronous satellite applications.
• This network extends secure quantum communication to a large number of users over wide geographical areas.