Swarm optimization for adaptive phase measurements with low visibility

Adaptive feedback normally provides the greatest accuracy for optical phase measurements. New advances in nitrogen-vacancy-center technology have enabled magnetometry via individual spin measurements, which are similar to optical phase measurements but with low visibility. The adaptive measurements that previously worked well with high-visibility optical interferometry break down and give poor results for nitrogen-vacancy-center measurements. We use advanced search techniques based on swarm optimization to design better adaptive measurements that can provide improved measurement accuracy with low-visibility interferometry, with applications in nitrogen-vacancy-center magnetometry.