A Ramsey-based wide-field magnetic imager using NV-diamond

We demonstrate a Ramsey-based wide-field magnetic imager employing a high density layer of nitrogen-vacancy (NV) color centers at the surface of a diamond chip. Three extensions to standard Ramsey sensing are employed to significantly enhance the sensitivity of the imager. First, we sense in the NV center double-quantum basis \textbraceleft -1,$+$1\textbraceright to eliminate common-mode noise sources, such as crystal-lattice strain fields. Second, we control the diamond bath spins to extend the effective sensing time, which is typically limited by interactions with an inhomogeneous spin environment. Lastly, we deploy a double-differential noise cancellation scheme for effective noise rejection and mitigation of pulse errors caused by inhomogeneities of the applied MW fields.