Fig. 1. Conceptual and experimental scheme. (a) Three-level Cs atom energy diagram;(b) Schematic of experiment equipment

Fig. 2. EIT-AT and AC Stark effect

Fig. 3. Difference-frequency signal as a function of local oscillator radio frequency (RF)

Fig. 4. Impact of local oscillator RF field on output signal-to-noise ratio (SNR). (a) SNR of difference-frequency signal as a function of difference frequency; (b) SNR of difference-frequency signal as a function of local oscillator RF power

Fig. 5. Relationship between measured signal power and difference-frequency signal power in superheterodyne detection

Fig. 6. Signal response curves based on atomic superheterodyne. (a) Minimum detectable field in frequency range of 1–40 GHz;(b) Minimum detectable field in frequency range of 110–170 GHz^[35], different color represents the usage of Rydberg state