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arXiv · 2509.13486

A $^{3}$He-$^{21}$Ne Ramsey Comagnetometer with sub-nHz frequency resolution

Shaobo Zhang·Jingyao Wang·George Sun·Johannes J. van de Wetering·Michael V. Romalis
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Abstract

Nuclear spin comagnetometers offer exceptional precision in measurements of spin energy levels and exhibit long-term stability, making them powerful tools for probing spin-dependent physics beyond the Standard Model as well as for inertial rotation sensing. We describe a new $^{3}$He-$^{21}$Ne Ramsey comagnetometer operating with an in-situ $^{87}$Rb magnetometer for initialization and sensing of nuclear spins. During free precession of nuclear spins we turn off all lasers and introduce a microwave field to suppress back-action from Rb atoms. We demonstrate that scalar and dipolar interactions between nuclear spins can be eliminated via control of the polarized sample geometry. These improvements result in a bias-free measurement with a frequency sensitivity of 0.6 nHz after 6 hours of integration.

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Shaobo Zhang, Jingyao Wang, George Sun, Johannes J. van de Wetering, Michael V. Romalis. 2025-09-16. A $^{3}$He-$^{21}$Ne Ramsey Comagnetometer with sub-nHz frequency resolution. https://arxiv.org/abs/2509.13486

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