Anomalous Long-Distance Coherence in Critically-Driven Cavity Magnonics

TL;DR

This paper demonstrates long-distance quantum coherence in cavity magnonics by exploiting critical coupling phenomena, revealing anomalous coupling behaviors over a 2-meter distance that challenge conventional theories.

Contribution

It introduces a novel approach to establish non-local magnon-photon coherence using critical coupling in cavity magnonics, uncovering unexpected anomalies in coupling dynamics.

Findings

Observation of long-distance magnon-photon coherence over 2 meters

Detection of coupling strength oscillations twice the conventional period

Identification of mode splitting within the cavity linewidth

Abstract

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.