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

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.