Resolving Quanta in Magnet　
Quantitative characterization of a quantum behavior in a magnet using an elementary device for quantum computing

The research group led by Professor Yasunobu Nakamura at the Research Center of Advanced Science and Technology, and Research Associate Yutaka Tabuchi demonstrated that quanta of the collective spin motions in a magnet, called a “magnon”, could be resolved. Up to now, there was no existing method to quantify the collective spin motions at the single-quantum level. The research group measured the number distribution of magnons excited in a ferromagnetic single-crystalline sphere by using a quantum bit based on a superconducting circuit (superconducting qubit) as a highly-sensitive detector. Superconducting qubits are widely recognized as an elementary device for future quantum computing.

The result showed that superconducting qubit devices could be a new type of detector for quantum-mechanical behaviors of a matter through quantum coherent hybridization between the superconducting qubit and the target. Our hybrid quantum system merging superconducting quantum bits and other quantum systems will lead to novel sensor technologies and advanced quantum information technologies.

This study was conducted in collaboration with the Center for Emergent Matter Science, RIKEN. It was partially supported by the Strategic Basic Research Programs of the Japan Science and Technology Agency (JST) as a project covering "ERATO NAKAMURA Macroscopic Quantum Machines".

Paper

"Resolving quanta of collective spin excitations in a millimeter-sized ferromagnet", Science Advances

Dany Lachance-Quirion, Yutaka Tabuchi, Seiichiro Ishino, Atsushi Noguchi, Toyofumi Ishikawa, Rekishu Yamazaki, Yasunobu Nakamura

DOI :10.1126/sciadv.1603150