China achieves 540km chip-based quantum communication breakthrough to scale secure networks

China’s research teams have built a long-distance chip-based quantum communication network and realised secure key transmission across a 540-kilometre optical fibre link, with relevant findings published online in the international journal Nature Photonics. The milestone addresses two core technical bottlenecks restricting the large-scale deployment of quantum communication technology, namely long-distance stable transmission and scalable network construction.

Quantum communication derives its core security performance from the quantum no-cloning theorem, which prevents precise duplication of unknown quantum states. Quantum key distribution enables secure key sharing between users, and paired with one-time-pad encryption, delivers theoretically unconditional information security. Unlike classical optical signals that can be amplified and retransmitted to extend transmission range, single-photon quantum signals weaken rapidly over distance and cannot be copied or amplified, creating major barriers to long-distance quantum communication.

Quantum repeater technology has become a core solution to break distance limits, leveraging quantum entanglement, entanglement swapping and quantum storage to achieve long-range signal transmission. Chinese researchers have laid foundational frameworks for global quantum repeater development. The DLCZ quantum repeater scheme proposed by domestic scholars in 2001 has become an industry-standard framework, providing feasible technical pathways for global experimental research in this field.

Current technical optimisation focuses on two major dimensions to expand transmission boundaries. Continuous upgrades to quantum key distribution protocols and system design improve detector performance, reduce operational noise and enhance error correction efficiency, pushing practical system performance closer to theoretical limits. Iterative breakthroughs in quantum repeater technologies further eliminate distance constraints for fibre-optic quantum communication.

Domestic research teams have made steady progress in practical core technologies. In early 2026, scalable basic modules for quantum repeaters were developed for the first time globally, achieving high-fidelity entanglement distribution between single-atom nodes. The innovation extended the transmission distance of device-independent quantum key distribution beyond 100 kilometres, greatly advancing the practicalisation of high-security quantum communication systems.

Beyond single-point long-distance transmission, quantum communication is shifting from point-to-point connection modes to multi-node networked architectures to support mass terminal access. Quantum communication networks adopt a three-tier structure consisting of backbone networks, metropolitan area networks and access networks. Backbone networks prioritise long-distance intercity point-to-point transmission, while metropolitan and access networks adopt point-to-multipoint frameworks to serve large-scale user terminals and improve overall resource utilisation.

China has completed systematic exploration and verification across all network tiers. A world-first space-ground integrated quantum communication network has been established, combining the Micius quantum science satellite with the 2,000-plus-kilometre Beijing-Shanghai trunk fibre quantum key distribution network, enabling coordinated networking between satellite and ground fibre links and validating technical pathways for future global quantum network construction.

In access network scenarios, innovative continuous-variable quantum key distribution point-to-multipoint protocols have been developed. The new protocols maintain full communication security while significantly boosting network efficiency. A 30-kilometre continuous-variable quantum key distribution access network has been built, completing multi-user networking verification covering 4, 8 and 16 terminal nodes.

Quantum communication stands as the most mature industrial segment in modern quantum information technology after two decades of iterative development. The progress in long-distance transmission and network construction has laid solid foundations for large-scale commercial adoption. The technological breakthroughs deliver value beyond secure communication, supporting distributed quantum cloud computing to enhance overall computational power and enabling long-distance quantum detector interconnection for ultra-precise detection and high-accuracy global time service systems.

Deep integration with traditional communication infrastructure has become a key direction for industrial iteration. Integrated quantum optical transmission network solutions have been rolled out in domestic commercial scenarios, enabling the co-carriage of classical communication services and quantum key distribution services on existing optical fibre networks.

Further industrialisation requires sustained breakthroughs in multiple technical links, including cost reduction and miniaturisation of core equipment, optimisation of multi-user networking protocols and practical quantum repeater engineering. Future research and industrial development will focus on deeper integration with existing information infrastructure, continuous reduction of deployment costs and improved large-scale networking capabilities, accelerating the integration of quantum key distribution systems into next-generation national information infrastructure.