Budker is a pioneer of optically pumped atomic magnetometry, having developed SERF and other high-sensitivity vapor-cell magnetometers used across fundamental-symmetry tests, the GNOME global magnetometer network searching for exotic physics, and the CASPEr NMR-based search for axion dark matter. This body of work sits alongside, and directly informs, the field of NV-diamond ensemble sensing (DEER, NMR, T1 relaxometry) that has reached pT/sqrt(Hz)-class sensitivities, since Budker's atomic-vapor techniques set many of the benchmark protocols that solid-state spin sensors now aim to match or exceed.

Romalis develops ultra-sensitive alkali-vapor magnetometers operating in the spin-exchange-relaxation-free (SERF) regime, K-noble-gas nuclear spin co-magnetometers used as gyroscopes and for electron/nuclear EDM and Lorentz-violation searches, and Rydberg-atom microwave electric-field sensors; his group's SERF magnetometers were the first used to detect brain magnetic fields. This continues and extends the historical arc of atomic and NV-ensemble quantum sensing (comparable in spirit to DEER/NMR/T1-relaxometry approaches reaching pT/sqrt(Hz) sensitivities), pushing scalar and vector magnetometry toward the fT/sqrt(Hz) and below regime through spin-squeezing and multi-pass optical cells.