Dispersive readout of room-temperature ensemble spin sensors

We demonstrate dispersive readout of the spin an ensemble Nitrogen-Vacancy centers in a high-quality dielectric microwave resonator at room temperature. The state is inferred from reflection phase signal probing resonator. Time-dependent tracking demonstrated, and employed to measure T1 relaxation time ensemble. Dispersive provides interface solid spins, translating into shift. estimate that its sensitivity can outperform optical schemes, owing high accuracy achievable measurement phase. scheme moreover applicable optically inactive defects it non-destructive, which renders insensitive several systematic errors enables use quantum feedback.