Satellite-based quantum communication is a promising approach for realizing global-scale quantum networks. For free-space quantum channel, single-mode fiber coupling is particularly important for improving signal-to-noise ratio of daylight quantum key distribution (QKD) and compatibility with standard fiber-based QKD. However, achieving a highly efficient and stable single-mode coupling efficiency under strong atmospheric turbulence remains experimentally challenging. Here, we develop a single-mode receiver with an adaptive optics (AO) system based on a modal version of the stochastic parallel gradient descent (M-SPGD) algorithm and test its performance over an 8 km urban terrestrial free-space channel. Under strong atmospheric turbulence, the M-SPGD AO system obtains an improvement of about 3.7 dB in the single-mode fiber coupling efficiency and a significant suppression of fluctuation, which can find its applications in free-space long-range quantum communications.
Cite
@article{arxiv.2012.04394,
title = {Single-mode fiber coupling with a M-SPGD algorithm for long-range quantum communications},
author = {Kui-Xing Yang and Maimaiti Abulizi and Yu-Huai Li and Bo-Yang Zhang and Shuang-Lin Li and Wei-Yue Liu and Juan Yin and Yuan Cao and Ji-Gang Ren and Cheng-Zhi Peng},
journal= {arXiv preprint arXiv:2012.04394},
year = {2020}
}