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.