Fiber-optic vectorial magnetic-field gradiometry by a spatiotemporal differential optical detection of magnetic resonance in nitrogen-vacancy centers in diamond.

Highly sensitive room-temperature vectorial magnetic-field gradiometry is demonstrated using optically detected magnetic resonance (ODMR) in fiber-coupled nitrogen-vacancy (NV) centers in diamond. With a bulk NV-diamond magnetometer coupled to a pair of optical fibers integrated with a microwave transmission line, the differential ODMR measurements are implemented in both space and time, with magnetic-field gradient measurements supplemented with differential ODMR signal detection in the time domain, allowing efficient noise cancellation and providing a sensitivity of magnetogradiometry at the level of 10  nT/(nmHz).