Chromatic effects in beam wander correction for free-space quantum communications

TL;DR

This paper investigates whether chromatic effects impact beam wander correction in free-space quantum communications, demonstrating experimentally that wavelengths around 850 nm and 1550 nm are similarly affected by atmospheric turbulence, enabling effective correction.

Contribution

The study provides experimental evidence that chromatic effects are negligible between 850 nm and 1550 nm wavelengths for beam wander correction in quantum communication.

Findings

Wavelengths at 850 nm and 1550 nm are equally affected by atmospheric turbulence.

Chromatic effects do not significantly impair beam wander correction at these wavelengths.

Experimental validation supports using different wavelengths for quantum signal and tracking in free-space links.

Abstract

Beam wander caused by atmospheric turbulence can significantly degrade the performance of horizontal free-space quantum communication links. Classical beam wander correction techniques cannot be applied due to the stronger requirements of transmitting single photons. One strategy to overcome this limitation consists in using a separate wavelength from that of the quantum signal to analyze the beam wander and use this information for its correction. For this strategy to work adequately, both wavelengths should be affected equally by atmospheric turbulence, i.e. no chromatic effects should be originated from beam wander. In this letter, a series of experiments are performed to prove that this is the case for {\lambda} ~ 850 nm as the quantum signal and {\lambda} ~ 1550 nm as the tracking signal of a quantum communication system.