We demonstrate dispersive readout of the spin of an ensemble of Nitrogen-Vacancy centers in a high-quality dielectric microwave resonator at room temperature. The spin state is inferred from the reflection phase of a microwave signal probing the resonator. Time-dependent tracking of the spin state is demonstrated, and is employed to measure the T1 relaxation time of the spin ensemble. Dispersive readout provides a microwave interface to solid state spins, translating a spin signal into a microwave phase shift. We estimate that its sensitivity can outperform optical readout schemes, owing to the high accuracy achievable in a measurement of phase. The scheme is moreover applicable to optically inactive spin defects and it is non-destructive, which renders it insensitive to several systematic errors of optical readout and enables the use of quantum feedback.
@article{arxiv.2003.07562,
title = {Dispersive Readout of Room Temperature Spin Qubits},
author = {J. Ebel and T. Joas and M. Schalk and A. Angerer and J. Majer and F. Reinhard},
journal= {arXiv preprint arXiv:2003.07562},
year = {2021}
}