The techniques of microwave quantum optics are applied to collective spin excitations in a macroscopic sphere of ferromagnetic insulator. We demonstrate, in the single-magnon limit, strong coupling between a magnetostatic mode in the sphere and a microwave cavity mode. Moreover, we introduce a superconducting qubit in the cavity and couple the qubit with the magnon excitation via the virtual photon excitation. We observe the magnon-vacuum-induced Rabi splitting. The hybrid quantum system enables generation and characterization of non-classical quantum states of magnons.
@article{arxiv.1508.05290,
title = {Quantum magnonics: magnon meets superconducting qubit},
author = {Yutaka Tabuchi and Seiichiro Ishino and Atsushi Noguchi and Toyofumi Ishikawa and Rekishu Yamazaki and Koji Usami and Yasunobu Nakamura},
journal= {arXiv preprint arXiv:1508.05290},
year = {2016}
}