Developing quantum networks necessitates coherently connecting distant systems via remote strong coupling. Here, we demonstrate long-distance coherence in cavity magnonics operating in the linear regime. By locally setting the cavity near critical coupling with travelling photons, non-local magnon-photon coherence is established via strong coupling over a 2-meter distance. We observe two anomalies in this long-distance coherence: first, the coupling strength oscillates twice the period of conventional photon-mediated couplings; second, clear mode splitting is observed within the cavity linewidth. Both effects cannot be explained by conventional coupled-mode theory, which reveal the tip of an iceberg of photon-mediated coupling in systems under critical driving. Our work shows the potential of using critical phenomena for harnessing long-distance coherence in distributed systems.
@article{arxiv.2404.13190,
title = {Anomalous Long-Distance Coherence in Critically-Driven Cavity Magnonics},
author = {Ying Yang and Jiguang Yao and Yang Xiao and Pak-Tik Fong and Hoi-Kwan Lau and C. -M. Hu},
journal= {arXiv preprint arXiv:2404.13190},
year = {2024}
}