Robust optical readout and characterization of nuclear spin transitions in nitrogen-vacancy ensembles in diamond

Nuclear spin ensembles in diamond are promising candidates for quantum sensing applications, including rotation sensing. Here we characterize the optically detected nuclear spin transitions associated with the N14 nuclear spin within diamond nitrogen-vacancy (NV) centers. We observe that the contrast of the nuclear-spin-dependent fluorescence is comparable to the contrast of the NV electron-spin-dependent fluorescence. Using Ramsey spectroscopy, we investigate the temperature and magnetic field dependence of the nuclear spin transitions in the 77.5-420 K and 350-675 G range, respectively. The nuclear quadrupole coupling constant Q was found to vary with temperature T, yielding d|Q|/dT=-35.0(2)Hz/K at T=297K. The temperature and magnetic field dependencies reported here are important for quantum sensing applications such as rotation sensing and potentially for applications in quantum information processing.