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Laser & Photonics Review

A Fully‐Connected Chip‐Integrated Reconfigurable Mode‐Pairing Quantum Key Distribution Network

Xiao-Lei Jiang, Wei Gao, Yan‐Yang Zhou, Yu Zhou, Yuyao Guo, Yifei Lu, Yuan‐Chao Yu, Yang Wang, Jia‐Ji Li, Chun Zhou, Hong‐Wei Li, Liangjun Lu, Linjie Zhou, Jian‐Ping Chen, Wan‐Su Bao

Published Aug 1, 2026• 1 citation
Publisher

Abstract

ABSTRACT Quantum key distribution (QKD) provides an information‐theoretic security framework for building QKD networks (QNs). However, existing QN architectures face critical challenges: trusted‐node‐based designs inherently expose relay nodes to physical compromise, while entanglement‐based approaches suffer from high implementation costs of sources. Here, this work proposes and conceptually validates a fully‐connected chip‐integrated reconfigurable QN based on the mode‐pairing (MP) QKD protocol. By combining hybrid‐integrated external‐cavity laser (ECL) chips with wavelength selective switch (WSS) chips, this architecture enables simultaneous secure key sharing among arbitrary users using only two wavelengths through a wavelength‐path dynamic resource allocation mechanism. Compared to conventional QN architectures, this approach significantly reduces the required port count and wavelength resources while supporting flexible reconfiguration such as on‐demand secure key supplementation and rapid reconstruction of faulty links‐capabilities unattainable in existing schemes. Experimental results demonstrate that the system achieves an average finite‐size secret key rate (SKR) of 5.72 kbps for each user pair under a channel loss of 40 dB. The compact design, cost‐effectiveness, and scalability of this architecture establish a robust foundation for the deployment of practical QNs.

DOI
10.1002/lpor.71642

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We report on the design and field validation of a fully connected entanglement-based quantum key distribution (QKD) network employing a time-shared photon-pair source and reconfigurable optical switching. The system eliminates the need for trusted relay nodes and enables any-to-any secure connectivity among users over metropolitan-scale fiber infrastructure. We present a three-node prototype network operating in the O-band(1310/1316nm)(1310 / 1316 \text{nm})(1310/1316nm)which demonstrates key generation sufficient to provide pairwise 10 G encrypted connections between 32 users, and confirming practical feasibility for telecom integration.
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Integrated silicon photonics offers a promising route toward compact and CMOS-compatible quantum key distribution (QKD) systems. However, on-chip laser integration remains a key barrier to full system miniaturization. Here, we demonstrate a fully integrated photonic device that combines an external-cavity laser (ECL) with a QKD transceiver, enabled by hybrid III-V/silicon photonic integration. The integrated transmitter and the phase-decoding receiver are combined to form a phase-encoded QKD system that demonstrates quantum bit error rates (QBER) of 1.4% (Z-basis) and 6.4% (X-basis), and a secure key rate of 28.16 kbps over a fiber channel with 8.3 dB loss at 625 MHz. The integrated system achieves a wavelength tunability of 87.61 nm, addressing the challenge of light source integration in silicon-based QKD networks. The demonstrated integration platform represents a crucial step toward the practical integration of QKD into existing optical transport networks (OTNs) and future quantum communication networks.
Abstract Quantum key distribution (QKD) promises unconditionally information‐theoretic secure communication guaranteed by the laws of physics and has become one of the most crucial candidates in future security aspects. Developing a large‐scale network with a scalable and integrated scheme is of great significance for expanding the advantages of QKD protocols among multiple users. Here, a sixteen‐user fully connected quantum network by using a novel time‐bin entangled source implemented in the integrated multi‐channel periodically poled lithium niobate waveguides is proposed. Based on this entangled source, the quantum processor prepares 120 entangled photon pairs to allocate 15 links to each user by utilizing dense wavelength division multiplexing technology. To enable the users’ communication with each other simultaneously, a phase‐compensated Mach‐Zehnder Interferometer based on a Fourier‐transform setup to control the relative phase of the interferometer for all the involved wavelength channels is developed. The experimental results show that the network can support sixteen users for long‐distance communication with each other simultaneously. The novel scheme of time‐bin entangled sources paves an efficient way for implementing large‐scale quantum resources in a compact integrated platform, and the time‐bin entangled network promises a new potential for constructing large‐scale and extensible quantum networks with an integrated photonic architecture.