CV-MDI Quantum Key Distribution via Satellite

TL;DR

This paper analyzes a satellite-based measurement-device-independent continuous-variable quantum key distribution protocol, demonstrating its potential to generate positive key rates over high-loss atmospheric channels even with untrusted satellites.

Contribution

It introduces a novel MDI CV-QKD protocol via satellite, analyzing security and key rates over atmospheric-fading channels with an untrusted relay satellite.

Findings

Positive key rates achievable over high-loss channels

Fading channels can enhance key rates under certain conditions

Untrusted satellite relays still enable secure key generation

Abstract

In this work we analyze a measurement-device-independent (MDI) protocol to establish continuous-variable (CV) quantum key distribution (QKD) between two ground stations. We assume communication occurs between the ground stations via satellite over two independent atmospheric-fading channels dominated by turbulence-induced beam wander. In this MDI protocol the measurement device is the satellite itself, and the security of the protocol is analyzed through an equivalent entanglement-based swapping scheme. We quantify the positive impact the fading channels can have on the final quantum key rates, demonstrating how the protocol is able to generate a positive key rate even over high-loss atmospheric channels. This is somewhat counter-intuitive given that the same outcome is only possible in the low-loss regime for a measurement device centrally positioned in a fiber-optic channel. Our results show that useful space-based quantum key generation rates between two ground stations are possible even when the relay satellite is held by an adversary. The cost in key rate incurred by altering the status of the satellite from trustworthy to untrustworthy is presented.