Correlated comagnetometry for precision measurements

Magnetometers are among the most widely used probes in science and technology. Comagnetometers increase sensitivity by self-cancellation of magnetic noise, but only at low frequencies. We suggest a correlated measurement of two alkali species in one cell to cancel the magnetic background also at high frequencies. The inter-species phase difference of the light-matter interaction response function is found to be calibration free and insensitive to common-mode intensity noise. Utilizing a dark-matter signal as a testcase, the method achieves a thirtyfold background suppression, raising the signal-to-noise ratio by an order of magnitude or more, depending on the coupling to the different subatomic particles. We show that the method also provides model differentiation. The higher sensitivity and model differentiation open a path to novel probes for precision measurements in general and exotic fields in particular.