How to implement decoy-state quantum key distribution for a satellite uplink with 50 dB channel loss

TL;DR

This paper demonstrates a quantum key distribution system capable of functioning with up to 57 dB of loss, enabling satellite uplinks and high-loss free space QKD links using innovative photon sources and timing analysis.

Contribution

It introduces a novel QKD implementation that overcomes high transmission losses, making satellite uplink QKD feasible with simplified receiver payloads.

Findings

Handles up to 57 dB photon loss in the infinite key limit

Uses weak coherent pulses and decoy states for high-loss regime

Confirms viability of satellite uplink QKD with high losses

Abstract

Quantum key distribution (QKD) takes advantage of fundamental properties of quantum physics to allow two distant parties to share a secret key; however, QKD is hampered by a distance limitation of a few hundred kilometers on earth. The most immediate solution for global coverage is to use a satellite, which can receive separate QKD transmissions from two or more ground stations and act as a trusted node to link these ground stations. In this article, we report a system capable of performing QKD in the high loss regime expected in an uplink to a satellite using weak coherent pulses and decoy states. Such a scenario profits from the simplicity of its receiver payload, but has so far considered to be infeasible due to very high transmission losses (40 - 50 dB). The high loss is overcome by implementing an innovative photon source and advanced timing analysis. Our system handles up to 57 dB photon loss in the infinite key limit, confirming the viability of the satellite uplink scenario. We emphasize that while this system was designed with a satellite uplink in mind, it could just as easily overcome high losses on any free space QKD link.