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arXiv · 1610.00839

Resolving magnon number states in quantum magnonics

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

Collective excitation modes in solid state systems play a central role in circuit quantum electrodynamics, cavity optomechanics, and quantum magnonics. In the latter, quanta of collective excitation modes in a ferromagnet, called magnons, interact with qubits to provide the nonlinearity necessary to access quantum phenomena in magnonics. A key ingredient for future quantum magnonics systems is the ability to probe magnon states. Here we observe individual magnons in a millimeter-sized ferromagnet coherently coupled to a superconducting qubit. Specifically, we resolve magnon number states in spectroscopic measurements of a transmon qubit with the hybrid system in the strong dispersive regime. This enables us to detect a change in the magnetic dipole of the ferromagnet equivalent to a single spin flipped among more than $10^{19}$ spins. The strong dispersive regime of quantum magnonics opens up the possibility of encoding superconducting qubits into non-classical magnon states, potentially providing a coherent interface between a superconducting quantum processor and optical photons.

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Dany Lachance-Quirion, Yutaka Tabuchi, Seiichiro Ishino, Atsushi Noguchi, Toyofumi Ishikawa, Rekishu Yamazaki, Yasunobu Nakamura. 2016-10-04. Resolving magnon number states in quantum magnonics. https://doi.org/10.1126/sciadv.1603150

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