Quantum magnetometer #

I started working with SBQuantum and their team in 2018 on a portable diamond-based quantum magnetometer, a device that uses a nitrogen-vacancy (NV) doped diamond, green lasers and microwaves to measure the ambient magnetic field. At the time, we were working on the V2 prototype, which was a miniaturized version of the previous V1 modular version. This new PCB was the first single-board magnetometer at the company.

This internship led to my bachelor's capstone project, where we worked on creating a new, space-grade version of the board for Université de Sherbrooke's Canadian CubeSat Project team. I working mainly on project management and on the Phase-Locked Loop circuit (PLL), a pretty tough piece of RF circuitry that is used in pretty much every antenna communication system and which most electrical engineers prefer to buy as a finished module, myself included.

Magnetic fields are measured by shooting green light on a doped diamond to excite some of its electrons, applying a microwave field to spin them, then re-shooting the diamond with green light and reading the amplitude of the red light it emits. Yes, red light. A combination of the direction and strength of the magnetic field, as well as the microwave frequency, will change the amplitude of the red light output and allow for measurement of the ambient magnetic field.

Below are shown the 8x3 peaks of the calibration sequence. The peaks come in 4 pairs of 3 mini-peaks, split around a central 2.87 GHz frequency, one for each possible NV orientation in the diamond crystal lattice. The three mini-peaks come from a phenomenon called hyperfine splitting which, in short, means that the circuit works well enough to get actual measurements from it and not just a bunch of noise. It's... a little complicated.

In 2019 and 2020, I worked on the MagQuest Phase 2 and 3 proposals, where I led the writing of the proposal describing the design of a satellite mission to measure Earth's magnetic field to update the World Magnetic Model and built a few test benches for the magnetometer (V3 at the time) and some of its parts. SBQuantum currently has upcoming projects with the European Space Agency and the Canadian Space Agency.