Adaptive-optics-enabled quantum communication: A technique for daytime space-to-Earth links

TL;DR

This study demonstrates a daytime space-to-Earth quantum communication link using adaptive optics and spatial filtering, achieving high efficiency and low error rates under realistic atmospheric conditions for satellite-based quantum networks.

Contribution

It presents the first detailed experimental validation of adaptive optics in daytime quantum communication, optimizing atmospheric channel conditions for space-to-Earth links.

Findings

Adaptive optics significantly improved quantum channel efficiency.

Spatial filtering effectively reduced optical noise without narrow spectral filters.

High signal-to-noise ratios and low quantum-bit-error rates were achieved in daylight conditions.

Abstract

Previous demonstrations of free-space quantum communication in daylight have been touted as significant for the development of global-scale quantum networks. Until now, no one has carefully tuned their atmospheric channel to reproduce the daytime sky radiance and slant-path turbulence conditions as they exist between space and Earth. In this article we report a quantum communication field experiment under conditions representative of daytime downlinks from space. Higher-order adaptive optics increased quantum channel efficiencies far beyond those possible with tip/tilt correction alone while spatial filtering at the diffraction limit rejected optical noise without the need for an ultra-narrow spectral filter. High signal-to-noise probabilities and low quantum-bit-error rates were demonstrated over a wide range of channel radiances and turbulence conditions associated with slant-path propagation in daytime. The benefits to satellite-based quantum key distribution are quantified and discussed.