Magnetometry and vector electrometry with atoms in circular Rydberg states

Atoms in Rydberg states can act as highly sensitive, and minimally invasive probes of static electric and magnetic fields [1,2]. To characterize and minimize these fields in cryogenic, high vacuum environments - such as those encountered in precision spectroscopy experiments with antihydrogen, or those required to measure the absolute neutrino mass by cyclotron radiation emission spectroscopy (CRES) following beta decay of atomic tritium [3,4] - it is desirable to implement magnetometers and electrometers with atoms that are already present in the apparatus to avoid contamination or detrimental effects of surface adsorption, e.g., the antihydrogen or tritium atoms themselves. Or to use species that are inert or cause minimal contamination, e.g., atomic hydrogen or helium. Here we demonstrate the measurement, and 1D mapping (spatial resolution of ±1 mm over a distance of 40 mm) of static magnetic fields, and the minimization, and characterization of residual uncancelled static electric fields by a combination of microwave Ramsey spectroscopy of transitions between circular Rydberg states, and low-l Rydberg states in helium. Magnetic fields of 1.4 - 1.6 mT were measured to a relative precision of ±100 nT in a measurement time of 1 μs, with an absolute precision limited by Doppler shifts to ~1 μT. Residual uncancelled electric fields were determined in the x, y and z dimensions in the apparatus to an absolute precision of ±600 μV/cm. These results pave the way for atoms in circular Rydberg states to be used for electric and magnetic field mapping in experiments to measure the neutrino mass by CRES.

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[2] E. K. Dietsche, A. Larrouy, S. Haroche, J. M. Raimond, M. Brune and S. Gleyzes, Nat. Phys. 15, 326 (2019)

[3] B. Monreal and J. A. Formaggio, Phys. Rev. D 80, 051301 (2009)

[4] D. Asner et al., Phys. Rev. Lett 114, 162501 (2015)