Magnon-mediated entanglement of spin qubits via on- and off-resonant interactions*

The ability to manipulate entanglement between multiple qubits is essential in quantum information processing. While nitrogen-vacancy (NV) centers in diamond are a promising qubit platform, developing their two-qubit gates in a scalable fashion remains a well-known challenge. To this end, magnon-mediated long-distance entanglement schemes have been proposed and attracted attention [1,2]. Optimal device geometries and gate protocols, however, have yet to be explored. Here we first predict [3] strong long-distance NV-NV interactions via magnons in ferromagnet bar and waveguide structures. Moreover, we explore and compare on-resonant transduction and off-resonant virtual-magnon exchange protocols, and discuss which one is suitable to create entangled states under realistic experimental conditions. This work serves as a guide for future experiments that aim to entangle spin qubits in solids through magnon excitations.

[1] L. Trifunovic et al., Phys. Rev. X 3, 041023 (2013)
[2] D. R. Candido et al., Materials for Quantum Technology (2020) in press (arXiv:2003.04341)
[3] M. Fukami et al., in preparation