Surface-magnon mediated self-interaction of nitrogen-vacancy centers in diamond*

Hybrid quantum systems consisting of nitrogen-vacancy (NV) centers in diamond and magnons in ferrimagnets have recently attracted much attention as a platform for on-chip long-distance entanglement, interfacing quantum information science with magnonics [1,2]. Here, we experimentally determine the magnon-induced self-interaction of this hybrid system by combining longitudinal (T_1) relaxometry measurements with the fluctuation-dissipation and Kramers-Kronig relations. This self-interaction is a function of the NV-magnon coupling strength and thereby provides an estimate of the magnon-mediated two-qubit interaction. Our results, including the enhanced T_1 relaxation rates caused by magnetostatic surface magnons are quantitatively consistent with a model in which the NV center is coupled to magnons by the magnetic dipole interactions. These findings help build a foundation for the hybrid quantum architecture of spin qubits coupled to magnons.

[1] D. R. Candido, et al., Mater. Quantum. Technol. 1, 011001 (2021)

[2] M. Fukami, et al., PRX Quantum 2, 040314 (2021)