Sub-optical resolution of single spins using magnetic resonance imaging at room temperature in diamond

TL;DR

This paper demonstrates room-temperature magnetic resonance imaging of single NV spins in diamond with sub-optical wavelength resolution, enabling detailed imaging of individual quantum spins and their interactions.

Contribution

The authors develop a microwave MRI technique that achieves sub-optical resolution of single NV spins in diamond at room temperature, surpassing previous limitations.

Findings

Achieved resolution 1/270 of the microwave wavelength

Resolved magnetically equivalent NV spins below optical wavelength

Potential for imaging large NV ensembles and dark spins

Abstract

There has been much recent interest in extending the technique of magnetic resonance imaging (MRI) down to the level of single spins with sub-optical wavelength resolution. However, the signal to noise ratio for images of individual spins is usually low and this necessitates long acquisition times and low temperatures to achieve high resolution. An exception to this is the nitrogen-vacancy (NV) color center in diamond whose spin state can be detected optically at room temperature. Here we apply MRI to magnetically equivalent NV spins in order to resolve them with resolution well below the optical wavelength of the readout light. In addition, using a microwave version of MRI we achieved a resolution that is 1/270 size of the coplanar striplines, which define the effective wavelength of the microwaves that were used to excite the transition. This technique can eventually be extended to imaging of large numbers of NVs in a confocal spot and possibly to image nearby dark spins via their mutual magnetic interaction with the NV spin.