Building an NV Magnetometer for Application in the LANL nEDM Experiment

Greater precision in attempts to measure a non-zero neutron electric dipole moment (nEDM) provides further insight into possible causes of the universe’s matter-antimatter asymmetry and in turn provides a better understanding of the Standard Model. In a typical nEDM measurement, ultracold neutrons are observed in a combined electric and magnetic field. More precise knowledge of the magnetic field allows for a more precise measurement of the nEDM. A Nitrogen vacancy (NV) center is a defect in a diamond lattice where a N atom is in place of a C atom and an adjacent C atom is missing. This defect possesses a direct correlation between its optical properties and spin states, which makes it an excellent quantum sensor for magnetic (and electric) fields. Specifically, green light causes an NV center to fluoresce red; however, in the presence of microwaves (MW) at a frequency corresponding to the excitation energy of a Zeeman-shifted state, a fraction of the emitted light will be in the infrared spectrum. In continuous wave excitation, a MW source scans through a range of frequencies, and the resonant frequency is revealed by a minimum in fluorescence intensity. However, coherent control of the NV state is also possible using a timed sequence of laser and MW pulses, so techniques like Ramsey interferometry can be used for greater precision. Development of an NV magnetometer as a supplement for other types of magnetometers commonly used for nEDM experiments, such as fluxgates and SQUIDs, will be described.