Magnetometry based on electron spin defects

A magnetometer comprising:

• a sample signal device;
• a reference signal device;
• a microwave field generator arranged to apply a microwave field to the sample signal device and the reference signal device;
• an optical source configured to emit light comprising light of a first wavelength that interacts optically with the sample signal device and with the reference signal device;
• at least one photodetector arranged to detect a sample photoluminescence signal comprising light of a second wavelength emitted from the sample signal device and a reference photoluminescence signal comprising light of the second wavelength emitted from the reference signal device, wherein the first wavelength is different from the second wavelength;
• a magnet arranged adjacent to the sample signal device and the reference signal device;
• and
• a computer system coupled to the at least one photodetector and configured to receive light measurement signals corresponding to the sample photoluminescence signal and to the reference photoluminescence signal from the at least one photodetector,
• wherein the computer system is configured to differentiate between the light measurement signals corresponding to the sample photoluminescence signal and the light measurement signals corresponding to the reference photoluminescence signal by applying time-gated detection, and
• wherein the time-gated detection is based on different optical path lengths for (i) the light from the optical source directed to the sample signal device and (ii) the light from the optical source directed to the reference signal device.