Our sensor, the nitrogen-vacancy (NV) center, is a point defect in the diamond crystal and functions as an electron spin based quantum bit. This quantum bit can be used as a highly sensitive sensor to measure magnetic fields. Because of its atomically small size, these NV centers are among the world's smallest sensors, which enables sensing and imaging on the nanoscale. The wide range of working conditions: cryogenic to room temperature, vacuum to tens of GPa open up many possible applications for this quantum sensor. Here we demonstrate two such applications.

Firstly, nanoscale vector magnetic field imaging using a planar scanning probe. Planar scanning probe microscopy is a recently emerging alternative approach to tip-based scanning probe measurements. It allows scanning of an extended planar sensor, such as a polished bulk diamond doped with NV centers, in nanometer-scale proximity of a planar sample. We use this new ability to perform direct imaging of the three-dimensional vector magnetic field of a magnetic thin film heterostructure, based on repeated scanning with NV centers with different orientations within the same scanning probe. [1]

We also present three-dimensional magnetic resonance tomography with NV centers. This technique uses magnetic field gradients to determine the three-dimensional position of NV centers in a densely doped diamond with a resolution of 5.9 ± 0.1 nm. [2]

References
[1] P., Weinbrenner, Quantum Sci. Technol., 2024, 10, 015037
[2] M., T. Amawi, npj Quantum Inf., 2024, 10, 16