Circuit-QED emerged from coupling superconducting qubits to cavity photons. Extending this to spin qubits is challenging because microwave photons are too large. A promising alternative is magnons, the collective excitations of magnetically ordered solids. Magnons offer key advantages: they can be confined to much smaller volumes and naturally exhibit chirality. Here, we demonstrate a chiral magnonic cavity by observing strong coupling between molecular spin qubits and antiferromagnetic magnons with tunable symmetry: from linear to left-handed chiral.
