A flexible and resource-efficient quantum network enabled by integrated photonics

Quantum key distribution (QKD) is evolving toward large-scale metropolitan networks that interoperate with modern communication infrastructures. Although wavelength division multiplexing (WDM) architectures hold great promise for high secure-key throughput and multi-user access, existing implementations suffer from security vulnerabilities introduced by trusted nodes, limited topological flexibility, and high resource overhead. Here, we experimentally demonstrate a flexible and resource-efficient mode-pairing QKD network enabled by integrated photonics, which natively supports trusted-node-free networking. Each user employs a Hz-level ultra-narrow-linewidth hybrid-integrated laser chip paired with a high-speed thin-film lithium niobate modulator chip for quantum state preparation, while a silicon-based wavelength-selective switch chip is deployed at the detection center. By introducing a novel global network-management strategy, the network fully decouples conventional physical-topology connections from resource-allocation constraints, allowing dynamic adaptation to time-varying communication demands and dynamic user access/leave. It achieves secure key sharing among all users with at most three distinct wavelengths and \((N)\) Bell-state measurement units, delivering superior flexible scalability and resource-efficient full-connectivity compared with conventional WDM architectures. In a proof-of-principle three-user network, we achieve secure-key generation over both symmetric and asymmetric metropolitan hundred-kilometer-scale fiber-link configurations. Further point-to-point tests verify secure-key generation over 300 km with the asymptotic key rate exceeding the repeaterless bound. By combining photonic integrated circuits with a favorable network-management strategy, this work provides a chip-scale pathway toward compact, low-cost, and scalable large-scale metropolitan quantum networks.