A 300-km fully-connected quantum secure direct communication network.

Area of Science:

• Quantum communication networks
• Quantum information science
• Secure communication technologies

Background:

• Current quantum networks face limitations in transmission distance and user scalability.
• Simultaneously addressing distance and user capacity is a key challenge in quantum network construction.

Purpose of the Study:

• To propose and demonstrate a long-distance, large-scale, and scalable fully-connected quantum secure direct communication (QSDC) network.
• To overcome the limitations of existing quantum network technologies for practical applications.

Main Methods:

• Implementation of a novel double-pumped structure within the quantum network.
• Strategic introduction of extra noise to enhance network performance and security.
• Paired communication between four users over a 300 km transmission distance.

Main Results:

• Successful realization of QSDC over 300 km between four users.
• Maintained entangled state fidelity above 85% after communication.
• Demonstrated the viability of the proposed network architecture.

Conclusions:

• The developed QSDC network effectively addresses long-distance and scalability challenges.
• The findings provide a novel foundation for future large-scale quantum communication networks.
• This research validates a new approach for secure, long-range quantum communication.