Requirements for processing-node quantum repeaters on a real-world fiber grid

We numerically study the distribution of entanglement on a real-world fiber grid connecting the German cities of Bonn and Berlin realized with a chain of processing-node quantum repeaters spanning roughly 900 kilometers. We determine minimal hardware requirements for two quantum network applications, blind quantum computation and quantum key distribution starting from currently realized group-IV color center and trapped ion parameters. We investigate how the minimal hardware requirements depend on the currently achievable parameters, target application as well as on characteristics of the repeater chain such as number of nodes and their placement. We implement our repeater chain simulations using the discrete-event quantum network simulator NetSquid, which allows us to accurately track time-dependent noise and implement repeater chain protocols with cut-offs, including the required classical communication. We find minimal hardware requirements by solving an optimization problem using genetic algorithms on a high-performance-computing cluster. Our work sheds light on the path towards scaling quantum repeaters to distribute high-quality entanglement over hundreds of kilometers.