In a remarkable leap for quantum technology, Chinese researchers have constructed a quantum secure direct communication (QSDC) network spanning approximately 300 kilometers—the practical range for inter-city applications. This achievement marks a significant milestone in the field of quantum communication.
The team from Shanghai Jiao Tong University managed to maintain over 85% quantum state fidelity during transmission between pairs of users within the network. This high level of fidelity ensures that the quantum states remain intact over long distances, which is crucial for the security and reliability of quantum communications.
Published in the journal Science Bulletin, the research addresses two key limitations in current quantum networks: transmission distance and user capacity. By developing a double-pumped, expandable, and fully connected QSDC network that operates effectively even in noisy environments, the team has paved the way for more practical and widespread use of quantum communication technologies.
The system achieved a stable photon pair rate of 300 to 400 Hz, theoretically allowing for communication speeds of several bits per second. While this may seem slow compared to conventional communication methods, the unparalleled security offered by quantum communication makes it extremely valuable for sectors requiring high levels of information security, such as finance and government.
This breakthrough comes on the heels of other significant achievements in the field. In February, a team from Beijing set a record by conducting a quantum direct communication test via standard optical fiber over a distance of 104.8 kilometers.
Quantum secure direct communication, initially proposed by researchers from Tsinghua University, enables secure communication by utilizing quantum states and features like eavesdropping detection and prevention. It offers compatibility with existing networks, simplified management processes, and covert transmission capabilities.
These advancements are complementary to quantum key distribution (QKD), another type of quantum secure communication. Together, these technologies have the potential to form the backbone of a future global quantum internet.
In a world-first, an international team led by Chinese scientists recently demonstrated real-time QKD communication over more than 12,900 kilometers between China and South Africa using satellite technology. This achievement underscores China’s leading role in pushing the boundaries of quantum communication.
The continued development of quantum communication networks promises a new era of secure, high-speed communication, with far-reaching implications for global connectivity and information security.
