High-speed free-space quantum key distribution with automatic tracking for short-distance urban links

TL;DR

This paper presents a high-speed free-space quantum key distribution system for urban environments, focusing on automatic tracking, low error rates, and optimized source and detector selection to enhance security and reliability.

Contribution

It introduces a novel automatic tracking system and compares two beam wander compensation techniques tailored for different atmospheric conditions in urban quantum communication.

Findings

Successful implementation of high-speed quantum key distribution in urban settings

Effective beam wander compensation techniques for atmospheric turbulence

Enhanced security and stability in free-space quantum links

Abstract

High-speed free-space quantum key distribution located in urban environment offers an interesting alternative to public key encryption - whose security strength is yet to be mathematically proven. To achieve this, three main objectives need to be accomplished: both the emitter and receiver have to be capable of transmitting and receiving at high speed - with the selection of the source's wavelength and detectors being of especial importance - the error rate needs to be kept at a minimum, especially that due to solar background radiation; and finally, a fast automatic tracking system, capable of compensating for atmospheric turbulence effects, is needed. Regarding to sky background and atmospheric turbulence, two different tracking techniques involving the beam wander compensation in the emitter or the receiver are presented and one of them is selected for our system, based on the link propagation distance and the atmospheric turbulence regime.