Time-delayed single satellite quantum repeater node for global quantum communications

TL;DR

This paper proposes a novel single-satellite quantum repeater node with two quantum memories, significantly enhancing secure key generation for global quantum communication while reducing hardware complexity.

Contribution

It introduces a time-delayed single satellite quantum repeater node with two quantum memories, outperforming previous single-memory methods in secure key rate and hardware efficiency.

Findings

At least three orders of magnitude improvement in secure key generation

Reduced quantum memory capacity requirements

Feasible experimental platform using rare-Earth ion doped crystals

Abstract

Global-scale quantum networking faces significant technical and scientific obstacles. Quantum repeaters (QRs) have been proposed to overcome the inherent direct transmission range limit through optical fibre. However, QRs are typically limited to a total distance of a few thousand kilometres and/or require extensive hardware overhead. Recent proposals suggest that strings of space-borne QRs with on-board quantum memories (QMs) are able to provide global coverage. Here, we propose an alternative to such repeater constellations using a single satellite with two QMs that effectively acts as a time-delayed version of a single QR node. Using QKD as a benchmark, we estimate the amount of finite secure key generated and demonstrate an improvement of at least three orders of magnitude over prior single-satellite methods that rely on a single QM, while simultaneously reducing the necessary memory capacity similarly. We propose an experimental platform to realise this scheme based on rare-Earth ion doped crystals with appropriate performance parameters.