A read-out enhancement for microwave electric field sensing with Rydberg atoms

We have shown that Rydberg atoms can be used for high-sensitivity, absolute sensing of radio frequency (RF) electric fields.(1) We achieved a sensitivity of 3 mu Vcm(-1) Hz(-1/2) for two read-out strategies. Results using a Mach-Zehnder interferometer(2) and frequency modulated spectroscopy(3) both achieve similar photon shot noise limited sensitivity. Fundamental limits to the sensitivity of the Rydberg atom-based RF electric field sensing have been addressed.(4) Depending on the spectral resolution of the read-out, either the RF induced transmission line frequency splitting, the Autler-Townes regime, or a change in the on-resonant absorption, the amplitude regime, can be used to determine the RF electric field. Here, we present theoretical results of a 3-photon read-out scheme which enables the Autler-Townes regime of Rydberg atom-based RF electrometry to be extended to lower RF electric field strengths. We show that the residual Doppler shifts can, in principle, be reduced to similar to 11.8 kHz, on the order of the Rydberg atom natural linewidths, using the approach.