Rethinking quantum repeaters: balancing scalability, feasibility, and interoperability

Abstract Quantum repeaters are enabling technologies for long-distance quantum communications. Despite the significant progress in the field, we still not only face implementation challenges but also need theoretical solutions that better meet all the desired design criteria. Preliminary solutions for quantum repeaters often do not scale well, while the most advanced solutions are so demanding that their implementation may take a long time and require substantial changes to current telecom infrastructure. In this paper, we propose a compromise solution that is not only scalable in the mid-to-long term but also adapts well to the realities of the backbone networks in the current Internet infrastructure. The key ideas behind our solution are twofold. First, we use a hop-by-hop approach to entanglement swapping, allowing our solution to benefit from the same features as packet-switched networks. Second, we employ simple error detection, rather than more complicated error correction, techniques to make our solution sufficiently scalable in the face of errors. This is achieved without requiring overly demanding specifications for the physical devices needed in the network. We test this idea in a quantum key distribution (QKD) setting over a repeater chain and demonstrate how trust-free continental QKD can be achieved through several stages of development.