Next, they added a 150-micrometer-thick nitrogen-vacancy (NV) diamond layer, which allowed the sensor to detect tiny magnetic changes. This layer had a spin coherence time (T2) of 20 microseconds, meaning it could maintain quantum information long enough for accurate measurements.
Finally, they aligned the NV centers along specific directions within the diamond lattice. This resulted in a nitrogen defect concentration of eight parts per million (ppm), which is a key factor in quantum sensor performance.
Additionally, to improve accuracy, the research team added a tilt correction mechanism to adjust for small misalignments in the diamond crystal. This ensured the sensor performed well, like traditional diamond-based sensors. The diamond quantum sensor with NV centers was now ready for testing.