Optical Atomic Comagnetometry for Tests of Fundamental Physics*

Optical atomic magnetometry is widely used to search for physics beyond the Standard Model. However, uncontrollable magnetic fields can be a significant source of noise, reducing sensitivity and leading to systematic errors and false-positive signals. To mitigate these issues, comagnetometric methods have been implemented to limit the influence of magnetic fields and improve the sensitivity to nonmagnetic spin couplings.

The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is an international collaboration aiming to detect correlations in noise of magnetically-shielded optical spin sensors (e.g., optical magnetometers). The network particularly focuses on the detection of transient and oscillatory signals induced by ultralight bosonic dark matter. Although over the last years several measurement campaigns of the network were performed with optical atomic magnetometers, it has been speculated that further development of GNOME requires the construction and optimization of a sensor for the detection of transient and oscillatory non-magnetic signals.

We will report on our efforts in the development and characterization of a self-compensating atomic comagnetometer, a sensor first proposed by Michael Romalis and collaborators, which utilizes a mixture of alkali-metal vapors and a buffer gas. Implementation of these gases allows for efficient hybrid pumping of atoms and buffer gas, which, when combined with appropriate operating conditions, such as sample temperature, static magnetic field, and laser tuning, significantly enhances the sensitivity to non-exotic couplings by several orders of magnitude compared to traditional atomic magnetometers. Furthermore, we will present an analytical model that enables the calibration of the sensor for nonmagnetic couplings, based on studies of its magnetic response. Lastly, we will briefly discuss the operation of the sensor in the latest GNOME campaign.