A Large-Scale Reconfigurable Multiplexed Quantum Photonic Network

Abstract: Entanglement distribution in quantum networks will enable next-generation technologies for quantum-secured communications, distributed quantum computing and sensing. Future quantum networks will require dense connectivity, allowing multiple users to share entanglement in a reconfigurable and multiplexed manner, while long-distance connections are established through the teleportation of entanglement, or entanglement swapping. While several recent works have demonstrated fully connected, local multi-user networks based on multiplexing, extending this to a global network architecture of interconnected local networks remains an outstanding challenge. Here we demonstrate the next stage in the evolution of multiplexed quantum networks: a prototype global reconfigurable network where entanglement is routed and teleported in a flexible and multiplexed manner between two local multi-user networks composed of four users each. At the heart of our network is a programmable 8x8-dimensional multi-port circuit that harnesses the natural mode-mixing process inside a multi-mode fibre to implement on-demand high-dimensional operations on two independent photons carrying eight transverse-spatial modes. Our circuit design allows us to break away from the limited planar geometry and bypass the control and fabrication challenges of conventional integrated photonic platforms. Our demonstration showcases the potential of this architecture for enabling large-scale, global quantum networks that offer versatile connectivity while being fully compatible with an existing communications infrastructure.