Long-distance quantum communication sending single photons and keeping many

TL;DR

This paper proposes an all-optical quantum repeater system using fiber loop memories and quantum error correction, enabling long-distance quantum communication with single photons over thousands of kilometers.

Contribution

It introduces a novel quantum repeater design utilizing fiber loop memories and error correction codes, avoiding complex multi-photon entanglement or frequent error correction.

Findings

Effective for distances up to 10,000 km

Uses quantum error correction codes like GKP and Steane

Operates with single-photon states in classical fiber infrastructure

Abstract

Fiber-based classical communication is all-optical and uses light pulses reamplified and reshaped every 50-100 km in classical repeaters. Most compatible with this would be a quantum communication system which is also all-optical with quantum processing units placed in similar intervals. However, existing all-optical quantum communication protocols either require complicated quantum error correction steps for logical-qubit recoveries at every few kilometers or, over larger quantum repeater segments, they would at least depend on sharing complex multi-photon entangled states. Here we propose an all-optical memory-based quantum repeater for long-distance quantum communication, with quantum memories at each repeater station realized in the form of fiber loops combined with suitable quantum error correction codes for photon-loss protection. By sending only single-photon states through the fibers connecting the stations, such repeaters can operate in the classical infrastructure's long-segment regime. We analyze the performance of our scheme for the Gottesman-Kitaev-Preskill code, including a concatenation with the Steane code, as well as the single-photon quantum parity code for total distances up to 10000 km.