According to a study published Thursday in the journal Nature, Chinese researchers have developed the world's first large-scale quantum key distribution (QKD) network based on integrated photonic quantum chips.

This network supports parallel communication among 20 users, covering a total distance of 3,700 kilometers and achieving a global leading level in both user scale and network span.

QKD uses quantum states to transmit cryptographic keys, thereby ensuring secure communication. Twin-field QKD, which is suitable for long-distance quantum communication and supports resource sharing at the detector end, has emerged as an advanced form of QKD.

However, due to the extremely high performance requirements for light sources and modulation devices, the necessary hardware chip integration is difficult to achieve. As a result, this technology is primarily used in point-to-point QKD, whereas realizing a multi-user, large-scale network system poses considerable challenges.

A team led by Wang Jianwei from Peking University's School of Physics and Gong Qihuang, an academician of the Chinese Academy of Sciences, has developed a series of high-performance, fully integrated photonic quantum chips. Using these chips, they constructed a twin-field QKD network comprising 20 quantum chip nodes.

According to Wang, this is the world's first demonstration of a QKD network based on photonic quantum chips in more than two decades. Experiments showed that these chips exhibit high uniformity during wafer-level fabrication, enabling low-cost mass production. The work lays a technical foundation for building QKD networks that support longer distances and more users.

"Chip-based QKD networks represent a significant step toward system miniaturization and device practicality," Wang said, adding that high-performance, low-cost photonic quantum chips hold significant potential in advancing the practical application and large-scale deployment of quantum networks.

Reviewers from Nature noted that this work represents a significant advancement in quantum chip and network technology, and that the demonstrated quantum chip network exhibits remarkable scalability. "The article is undoubtedly of high impact for the quantum communication community," a reviewer commented.

Gong said this achievement provides a viable solution for constructing large-scale quantum communication chip networks and will promote the miniaturization, practical applications, and large-scale development of quantum communication systems.