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 traveling photons, nonlocal magnon-photon coherence is established via strong coupling over a 2-m 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 reveals the tip of an iceberg of photon-mediated coupling in systems under critical driving. Our Letter shows the potential of using critical phenomena for harnessing long-distance coherence in distributed systems.

中文翻译：

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临界驱动腔磁振子学中的反常长距离相干性

开发量子网络需要通过远程强耦合来连贯地连接遥远的系统。在这里，我们证明了在线性状态下运行的腔磁振子的长距离相干性。通过将腔局部设置为与行进光子接近临界耦合，可以通过 2 米距离上的强耦合建立非局部磁子-光子相干性。我们在这种长距离相干性中观察到两个异常现象：首先，耦合强度的振荡周期是传统光子介导耦合的两倍；其次，在腔线宽内观察到清晰的模式分裂。这两种效应都无法用传统的耦合模式理论来解释，该理论揭示了临界驱动下系统中光子介导耦合的冰山一角。我们的信展示了利用关键现象来利用分布式系统中的长距离一致性的潜力。