Optimal state choice for Rydberg atom microwave sensors

Rydberg electromagnetically induced transparency (EIT) enables the realization of atom-based Systeme-International-Traceable microwave sensing, imaging, and communication devices by exploiting the strong microwave electric dipole coupling of highly excited Rydberg states. Essential to the development of robust devices is a careful characterization of the sensor performance and systematic uncertainties. In this work, we present a comparison of microwave-induced EIT splitting in a cesium atomic vapor for four possible Rydberg couplings, 65S1/2→65P1/2, 66S1/2→66P3/2, 79D5/2→81P3/2, and 62D5/2→60F7/2, at microwave transition frequencies around 13 GHz. Our work highlights the impact of multiphoton couplings on neighboring Rydberg states in breaking both the symmetry and linearity of the observed splitting, with excellent agreement between experimental observations and a theoretical model accounting for multiphoton couplings. We identify an optimal angular-state choice for robust microwave measurements, as well as demonstrating an alternative regime in which microwave polarization can be measured.