Fig. 1. (a) The energy level diagram for the four-level system used for the experiment. The top part of the inset shows the EIT spectrum of a three-level system without a MW electric field. The bottom part of the inset shows the occurrence of AT splitting within the EIT window when a microwave electric field is applied^[1]; (b) The experimental setup for measuring electric fields using the Rydberg atom^[1]

Fig. 2. Detection of weak MW electric field^[1]. (a) The variation of EIT spectra with MW detuning under different electric field intensities; (b) The EIT spectrum changes with the amplitude of MW electric field for MW resonance

Fig. 3. (a) Schematic diagram of the radio communication experimental setup based on AT splitting ^[25]; (b) Change of AT splitting over time^[25]; (c) Up: Temporal comparison of the received signal and the transmitted signal. Bottom: Error between transmitted signal and received signal^[25]

Fig. 4. Research on radio communication based on EIT spectral height difference with/without communication signals^[26]. (a) EIT-AT split spectra; (b) Demodulation spectra; (c) Contrast of input phase and output phase; (d) Phase constellation of the received phase

Fig. 5. (a) Schematic of the the phase detection experimental setup with Rydberg atom-based mixer ^{[27, 29]}; (b) The measured beat note on the oscilloscope for different phase shifts of the signal field^[29]; (c) Constellation diagram of 64QAM^[27]

Fig. 6. Two measurement methods of instantaneous bandwidth: Measuring the rise time of the EIT signal and the 3 dB roll-off point of the frequency response^[11]

Fig. 7. (a) Spatiotemporal multiplexed Rydberg atomic antenna^[50]; (b) Experimental and numerical transmission profiles of probe pulses after passing through Rb vapor^[50]; (c) Experimental device diagram and energy level diagram of six-wave mixing scheme^[51]; (d) Experimental and theoretical instantaneous bandwidth^[51]

Fig. 8. At the same small size, the standard quantum limit of channel capacity and the channel capacity of traditional antennas. The black dots and pink line are experimental data and theoretical calculations, respectively^[47]