Dual tone RF dressing in Rydberg EIT for electric field sensing

Over the last decade, Rydberg electromagnetically-induced transparency (EIT) has been shown to be a versatile tool for sensitive electrometry in the radio frequency (RF) regime. These sensors have used the Rabi frequency-dependent Autler--Townes splitting of Rydberg energy levels driven by a single frequency RF field to characterize electric fields through their amplitude, phase, polarization, and more. Here we examine Rydberg EIT spectra in a configuration where the Rydberg atoms are dressed with a dual tone RF field. When the two RF frequencies are close to, but detuned from, a Rydberg resonance, the spectra reflect the more complex atomic response to the dual-field interaction than that observed with a single frequency RF dressing field. For instance, we can observe spectra where the separation between the peaks is controlled by detunings of the RF fields and is independent of the Rabi frequencies. We characterize the dual-tone dressed system through the Floquet quasi-energies and modes as we vary the frequencies and powers of the two RF fields independently. We discuss potential applications of the system, including the possibility of detecting the frequency and power of an unknown RF field and implications for Rydberg sensors in cluttered RF environments.