All-photonic quantum repeaters

TLDR

Quantum communication promises unconditionally secure transmission and faithful state transfer, but photon losses over long distances necessitate repeaters, and it is widely believed that such repeaters require matter quantum memories. The study demonstrates that quantum repeaters can be realized without matter memories by proposing all‑photonic repeaters using flying qubits. The authors present a protocol employing photonic cluster‑state machine guns and loss‑tolerant measurements with local high‑speed active feedforward. They show that all‑photonic repeaters achieve polynomial‑scaling efficiency with distance, opening a path to repeaters based on efficient single‑photon sources rather than matter memories.

Abstract

Abstract Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Photons appear to be the medium of choice for quantum communication. Owing to photon losses, robust quantum communication over long lossy channels requires quantum repeaters. It is widely believed that a necessary and highly demanding requirement for quantum repeaters is the existence of matter quantum memories. Here we show that such a requirement is, in fact, unnecessary by introducing the concept of all-photonic quantum repeaters based on flying qubits. In particular, we present a protocol based on photonic cluster-state machine guns and a loss-tolerant measurement equipped with local high-speed active feedforwards. We show that, with such all-photonic quantum repeaters, the communication efficiency scales polynomially with the channel distance. Our result paves a new route towards quantum repeaters with efficient single-photon sources rather than matter quantum memories.