Traditional NMR uses high magnetic fields to thermally polarize a small fraction of nuclei, thereby gaining information on the surrounding electronic enviroment. Here we probe a handful of nuclei within a very small volume, attempting to gain insight on structural conformality.
There are two principal architectures to extract the signal, whose names we can simplify to "active" and "passive".
The active method is reminiscent of NMR spectrometers, where one needs to flip the nuclei and measure the response of the system, whether these are electrons or nuclei, to it. It has been successfull demonstrated with the NV center in diamond already in 2013 [1], where the spin of hydrogen nuclei in PMMA was manipulated and sensed thereafter. In 2017, chemical shift resolution was demonstrated [2], showing the immense potential this technique could have for study of molecules.
[1] Mamin et al., Science 339, 557 (2013)
[2] Aslam et al., Science 357, 67 (2017)
The passive method has been explored in much greater detail, partially due to technical limitation of the active method and to a greater extent due to the strong correspondence between the schemes used to passively probe the nuclear spins and concepts from the quantum information processing community. These can be categorized under the umbrella of dynamic decoupling techniques, in which the experimental sequence in effect decouples the signal in question from the surrounding environment.