Micron-scale AC quantum sensing using nitrogen-vacancy centers in diamond*

Optically-probed nitrogen-vacancy (NV) quantum defects in a diamond, can optically detect AC magnetic signals with high-spectral resolution from micron-scale sample volumes. However, the performance of an ensemble NV sensor is limited by the magnetic field sensitivity of the device. We present a quantum memory readout technique for ensemble NVs that allows high-resolution micron-scale AC sensing with enhanced sensitivity. We also investigate the effect of the bias magnetic field and laser power on this measurement technique.