Comagnetometry using Synchronous Spin-Exchange Optical Pumping*

We present a spin-exchange pumped noble gas comagnetometer which utilizes two Xe isotopes and Rb atoms, all continuously polarized transverse to a pulsed bias field. The nuclear magnetic resonance conditions of both Xe species are simultaneously satisfied by frequency modulation of the pulse repetition rate, by modulation of the Rb polarization, or by a combination of the two. The Rb atoms, acting as an embedded magnetometer, detect the Xe precession. The demonstrated device achieves sub-µHz-scale rotation sensitivity, and suppresses sub-Hz magnetic field fluctuations by a factor of 2300.