Increasing the link-distance of free-space quantum coherent communication with large area detectors

TL;DR

This paper introduces a large area photodiode homodyne detector that enhances free-space quantum communication by improving signal collection efficiency over turbulent atmospheric channels, outperforming traditional fiber-based detectors.

Contribution

The study demonstrates the effectiveness of large area photodiodes in free-space quantum communication, reducing turbulence-induced signal loss compared to fiber-based detectors.

Findings

Large area photodiodes improve signal collection efficiency.

The detector experiences 0dB turbulence loss, versus 13.5dB for fiber-based detectors.

Enhanced performance over 700 km free-space links.

Abstract

We report a large area photo-diode based homodyne detector for free-space quantum coherent communication. The detector's performance is studied in terms of detection bandwidth and electronic noise for shot-noise limited quantum signal detection. Using large area photo-diodes increases signal collection efficiency from turbulent atmospheric channels, in comparison with typical fibre based free-space homodyne detectors. Under identical atmospheric turbulence and receiver aperture conditions, our homodyne detector based on 1mm diameter photo-diode experiences 0dB loss due to turbulence while a 10um fibre based detector experiences 13.5dB of signal loss over a 700km free-space link, at 90 degree elevation angle.