A large-scale reconfigurable multiplexed quantum photonic network

Abstract

The distribution of entanglement in quantum networks will enable the next generation of technologies in 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. Although several recent works have demonstrated fully connected, local multi-user networks based on multiplexing, extending such networks to a global network architecture of interconnected local networks remains an outstanding challenge. Here we demonstrate the next step in the evolution of multiplexed quantum networks—a prototype global reconfigurable network in which entanglement is routed and teleported in a flexible and multiplexed manner between two local four-user networks. At the heart of our network is a programmable 8 × 8-dimensional multi-port circuit that harnesses the natural mode-mixing process inside of 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 highlights 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. A reconfigurable eight-user photonic network is realized by connecting two local four-user networks through a programmable 8 × 8-dimensional multi-port device. Multiplexed routing and swapping of qubit entanglement are demonstrated for all network configurations and channels.