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Nature

Large-scale quantum communication networks with integrated photonics

Yun Zheng, Hanyu Wang, Xinyu Jia, Jiahui Huang, Huihong Yuan, Chonghao Zhai, Junhao Dai, Jingbo Shi, Lei Zhang, Xuguang Zhang, Minxue Zhuang, Jinchang Liu, Jun Mao, Tianxiang Dai, Zhaorong Fu, Yuqing Jiao, Yaocheng Shi, Daoxin Dai A, Xingjun Wang, Yan Li, Qihuang Gong, Zhiliang Yuan, Lin Chang, Jianwei Wang

Published Feb 11, 2026• 20 citations
Publisher

Abstract

Quantum key distribution (QKD) makes use of the principles of quantum mechanics to enable provably secure communication1,2. One substantial challenge persists in building large-scale QKD networks with many clients over long communication distances3. Although quantum relays continue to pose practical difficulties4, existing trusted-node networks5–9, point-to-multipoint networks10,11 and wavelength-multiplexed entanglement networks12,13 encounter issues such as reliance on trusted intermediaries or limited distances. Twin-field quantum key distribution (TF-QKD) provides a compelling architecture that can overcome those issues while enhancing communication distance14. Although long-distance point-to-point TF-QKD has been achieved15–21, realizing large-scale networks requires scalable quantum devices. Here we report a proof-of-principle demonstration of an integrated-photonics TF-QKD network with exceptional scalability and reliability. This network includes 20 independent client-side QKD transmitter chips with one server-side optical microcomb chip. The microcomb generates a broad range of ultralow-noise coherent frequency combs with Hz-level linewidths, which serve as seeds and references for all client chips. Each client chip regenerates ultralow-noise light phase-locked to microcombs and prepares quantum keys. We sequentially implement pairwise QKD across 20 client chips through ten wavelength-multiplexed channels, with each surpassing the repeaterless bound at 370 km in spooled fibre, achieving a networking capability (client pairs × communication distance) of 3,700 km. We further demonstrate the wafer-scale reproducibility of both server-side microcomb chips and client-side QKD transmitter chips, together establishing system-level scalability. Combining mass-manufacturability, cost-effectiveness and high scalability of integrated photonics with long-distance quantum communication represents a viable path to large-scale quantum networks. A lab-scale proof-of-principle demonstration of a quantum network comprising one server chip and 20 client photonic chips implementing twin-field quantum key distribution shows excellent scalability and reliability and yields a pathway towards future large-scale networks.

DOI
10.1038/s41586-026-10152-z

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Quantum key distribution (QKD) makes use of the principles of quantum mechanics to enable provably secure communication1,2. One substantial challenge persists in building large-scale QKD networks with many clients over long communication distances3. Although quantum relays continue to pose practical difficulties4, existing trusted-node networks5–9, point-to-multipoint networks10,11 and wavelength-multiplexed entanglement networks12,13 encounter issues such as reliance on trusted intermediaries or limited distances. Twin-field quantum key distribution (TF-QKD) provides a compelling architecture that can overcome those issues while enhancing communication distance14. Although long-distance point-to-point TF-QKD has been achieved15–21, realizing large-scale networks requires scalable quantum devices. Here we report a proof-of-principle demonstration of an integrated-photonics TF-QKD network with exceptional scalability and reliability. This network includes 20 independent client-side QKD transmitter chips with one server-side optical microcomb chip. The microcomb generates a broad range of ultralow-noise coherent frequency combs with Hz-level linewidths, which serve as seeds and references for all client chips. Each client chip regenerates ultralow-noise light phase-locked to microcombs and prepares quantum keys. We sequentially implement pairwise QKD across 20 client chips through ten wavelength-multiplexed channels, with each surpassing the repeaterless bound at 370 km in spooled fibre, achieving a networking capability (client pairs × communication distance) of 3,700 km. We further demonstrate the wafer-scale reproducibility of both server-side microcomb chips and client-side QKD transmitter chips, together establishing system-level scalability. Combining mass-manufacturability, cost-effectiveness and high scalability of integrated photonics with long-distance quantum communication represents a viable path to large-scale quantum networks. A lab-scale proof-of-principle demonstration of a quantum network comprising one server chip and 20 client photonic chips implementing twin-field quantum key distribution shows excellent scalability and reliability and yields a pathway towards future large-scale networks.
A scalable integrated-photonic twin-field quantum key distribution (TF-QKD) network is demonstrated. The system employs a star topology with a server-sideSi3 N4\text{Si}_{3} ~\mathrm{N}_{4}Si3​ N4​optical microcomb and 20 monolithically integrated InP transmitter chips. Coherent comb lines seed client lasers to enable wavelengthdivision multiplexed operation and stable interference. Sequential pairwise TF-QKD is implemented over ten channels among 20 users, each exceeding the repeaterless bound at 370 km. The networking capability reaches3,700 km3,700 ~\text{km}3,700 km(client pairs × distance), and wafer-scale chip reproducibility confirms a manufacturable platform for large-scale quantum communication networks.
Twin-field (TF) quantum key distribution (QKD) has been proved to overcome the linear rate-distance limit of repeaterless quantum communications and has the capability to generate high key rates over long distances compared with other QKD protocols. Photonic integration has proven a promising technique for the large-scale deployment of QKD. While it has been adopted to implement a range of linearly scaling QKD protocols, there is to date no demonstration of TF QKD using photonic integrated chips. One important challenge resides in establishing high coherence between remote laser chips. In this study, we exploit optical injection locking to implement phase dissemination to independent lasers integrated onto photonic circuits and further demonstrate complete phase control on the same chip using electro-optic phase modulators. We achieve high laser coherence between remote transmitter nodes, which lets us demonstrate a quadratic key-rate improvement of the secure key rate beyond 80 dB of channel attenuation. The experimental results are in excellent agreement with the theory in both finite size and asymptotic regimes, in which the fundamental rate-distance limit is overcome. Our work paves the way for the deployment of large-scale TF QKD networks enabled by compact, low-cost, and high-yield chip-based devices.
Twin-field quantum key distribution (TF-QKD) dramatically enhances the secure key rate (SKR) over inter-city distances through its square-root scaling. Further improvements in aggregate SKR can be achieved by wavelength-division multiplexing (WDM) of parallel QKD channels. However, direct implementation in TF-QKD poses significant challenges, as each wavelength channel requires an independent ultra-stable seed laser, narrow-linewidth transmitters, and optical phase-locked loops (OPLLs), which are not easily scalable. Here, we circumvent these limitations by employing two independent, integrated dissipative Kerr soliton (DKS) microcombs at Alice and Bob as multi-wavelength sources. High-visibility single-photon interference across all wavelength channels is achieved by stabilizing the frequencies of every comb line - requiring only the stabilization of the pump wavelength and repetition rates of the two microcombs. Based on this architecture, we perform a full TF-QKD experiment using the sending-or-not-sending protocol, achieving a total SKR of 1.57 Mbps over 201.1 km of fiber using 16 DWDM channels. This result represents more than an order-of-magnitude enhancement compared with single-wavelength TF-QKD at the same distance. Given that a single DKS comb can support over 100 coherent lines across the C-band, this approach offers a scalable pathway toward high-rate quantum key distribution over inter-city distances.
Quantum key distribution (QKD) is a key application in quantum communication, enabling secure key exchange between parties using quantum states. Twin-field (TF) QKD offers a promising solution that surpasses the repeaterless limits, and its measurement-device-independent nature makes it suitable for star-type network architectures. In this work, we propose a scalable TF-QKD network with adaptable architecture, where users prepare quantum signals and send them to network nodes. These nodes use an optical switch to route the signals to multi-user measurement units, enabling secure key distribution among arbitrary users and adapting to complex connection demands of the network. A proof-of-principle demonstration with three users successfully achieved secure key sharing over simulated link losses of up to 303030 dB, with an average rate of 19.5719.5719.57 bit/s. Additionally, simulations show that the proposed architecture can achieve a total secure key rate of 4.84×1044.84 \times 10^{4}4.84×104 bit/s at 100100100 km in a symmetric 323232-user network. This approach represents a significant advancement in the topology of untrusted-node QKD networks and holds promise for practical, large-scale applications in secure communication.
Abstract 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)(N)(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.
Quantum Key Distribution (QKD) enables information-theoretically secure cryptographic key exchange by exploiting quantum mechanical properties -- photon polarisation, entanglement, and the no-cloning theorem -- to detect any eavesdropping attempt. Scaling QKD from point-to-point laboratory demonstrations to large-scale metropolitan and wide-area networks requires addressing three engineering challenges: photon loss over long fibre distances (limiting practical QKD to ~100-150 km without quantum repeaters), network topology design for multi-party key delivery, and integration of QKD with classical network infrastructure. This paper proposes the Quantum Key Distribution Network Architecture (QKDNA) framework, a systematic evaluation of five QKD protocol families (BB84, E91, MDI-QKD, Twin-Field QKD, and CV-QKD) across four network topology models (star, ring, mesh, and hierarchical trusted-node) on 16 real-world metropolitan network scenarios. QKDNA achieves maximum secure key rate of 18.4 Mbps (Twin-Field QKD, 80 km fibre, mesh topology) and demonstrates scalable QKD delivery to 48 simultaneous users. The framework contributes a Network QKD Deployment Index (NQDI) and quantitative guidance for national quantum network infrastructure planning.