High-dimensional Quantum Networks: deploying the frequency and time modalities

Quantum networks enable fundamentally secure communications and entanglement distribution in parallelized quantum computation. Here we describe our high-dimensional quantum network based on frequency-multiplexed time-bin encoding. Our multi-user 21-km experimental testbed is designed for robustness and scalability, with frequency- and temporal-multiplexing for high-rate interconnects while preserving minimal resource usage and multi-party access through simultaneous key or entanglement distribution. Our measurements are in the high-dimensional frequency and temporal conjugate subspaces, via our biphoton frequency comb qudit. Non-local Franson interferometry provide a measured lower-bound of our entanglement-of-formation, and the Schmidt mode decomposition provide an estimate of the accessible quantum information. We highlight adaptive optimization and singly-filtered biphoton combs as a practical architecture in our high-rate quantum network testbed. We describe the photon information efficiency, Shannon capacity, entanglement distribution, raw key rates, security measurements, dispersive bases, code-efficient non-binary error correction, and Holevo bounds embedded in our network.