High-Spectral-Resolution NMR Using NV Centers in Diamond

Nitrogen-vacancy centers grown or implanted at the surface of a diamond chip can be used to detect nuclear magnetic resonance (NMR) signals from molecules in a small volume [\textless (10 nm)\textasciicircum 3 - (10 um)\textasciicircum 3] above the surface. A key outstanding challenge in the field is to achieve sufficient spectral resolution (\textasciitilde 1 ppm of the nuclear Larmor frequency) to distinguish features such as chemical shifts and J-couplings in the NMR spectra. We have developed a synchronized readout technique that satisfies this criterion for sample volumes on the order of \textasciitilde 1 pL. We show that this technique can provide mHz spectral resolution in the detection of an oscillating magnetic field (with carrier frequency f $=$ 4 MHz) produced by a nearby coil, and demonstrate progress towards the detection of molecular NMR spectra with resolved chemical shifts.