Fig. 1. General schematic of the atomic electric field sensor versus a standard receiver for sensing incident RF or microwave radiation^[62]

Fig. 2. Schematic diagram of the radio-optical measurement of two-photon excitation based on Rydberg atoms. (a) Experimental setup; (b) Experimental setup^[62]

Fig. 3. Transmission spectra of the probe laser under different external fields. (a) Only with the probe laser; (b) and (c) With the addition of control laser; (d) With further addition of RF or microwave fields^[62]

Fig. 4. Level scheme and experimental setup for Rydberg atomic optical measurement of a single-frequency static microwave electric field^[15]. (a) Level diagram of the four-level system, with the top inset showing the EIT spectrum when the microwave field is off and the bottom inset showing the EIT-AT spectrum when the microwave field is on; (b) Experimental setup

Fig. 5. Electric fields induced EIT and AT splitting in the probe laser transmission spectrum^[15]. (a) Corresponds to the weak field, while (b) corresponds to the modest field^[15]

Fig. 6. Enhancement of the EIT transparency peak of the transmission spectrum of the probe laser under the weak field^[15]. (a) EIT peak enhancement; (b) Physical mechanism behind the enhancement of EIT transmission

Fig. 7. Transmission spectrum induced by a weak microwave electric field^[15]. （a） Effect of the microwave field on the transmission spectrum of the probe laser; (b) Dependence of the EIT transparency peak height on the microwave electric field strength

Fig. 8. Schematic diagram of the radio-optical measurement heterodyne receiver based on Rydberg atoms^[20]

Fig. 9. Spectral processing procedure of the radio-optical measurement heterodyne receiver based on Rydberg atoms^[20]

Fig. 10. AC Stark shift effect under different field strengths, where (a) corresponds to weaker field strength and (b) corresponds to stronger field strength^[81]

Fig. 11. Schematic diagram of the electric field measurement of strong RF signals based on Rydberg atoms^[82]. (a) Experimental setup and level structure configuration; (b) Transmission spectrum of the probe laser

Fig. 12. EIT spectrum of the probe laser under strong ac fields^[82]. (a) EIT spectrum of Rydberg atoms coupled to a 50 MHz ac field as a function of field strength; (b) EIT spectrum of Rydberg atoms coupled to a 50 MHz ac field with an electric field intensity of 41.5 dBI; (c) EIT spectrum of Rydberg atoms coupled to ac fields at different frequencies with an electric field intensity of 46 dBI

Fig. 13. Schematic diagram of the signal demodulation process for Rydberg atomic wireless communication receiver (a) and traditional wireless communication receiver (b)^[95]

Fig. 14. Schematic diagram of the experimental setup for Rydberg atom wireless communication receiver based on single-frequency dynamic radio signal measurement^[61]

Fig. 15. Wireless communication receiver spectral processing based on single-frequency dynamic radio signal measurement^[61]. (a) EIT-AT spectrum; (b) Spectrum with 8 PSK modulation; (c) Phase comparison between input and output; (d) Trajectory of the output phase

Fig. 16. Wireless communication receiver channel capacity estimation based on single-frequency dynamic radio signal measurement. (a) Time-domain plot of the detected optical signal during communication reception; (b) and (c) Rising and falling edges at different pump rates; (d) Relationship between channel capacity and sampling rate^[61]

Fig. 17. Schematic diagram of the dual-band communication reception experiment^[75]

Fig. 18. Experimental setup for simultaneously measuring five microwave fields based on Rydberg atoms ^[92]. (a) Energy level structure; (b) Equipment configuration; (c) EIT spectrum

Fig. 19. Simultaneous amplitude and phase recovery for five microwave fields based on Rydberg atoms^[92]

Fig. 20. Spectrum and bandwidth analysis of EIT output for simultaneous multiband measurement of five radio-frequency signals based on Rydberg atoms^[92]

Fig. 21. Experimental setup for optical measuring multifrequency radio signals and communication demonstration using deep learning model based on Rydberg atoms^[100]

Fig. 22. Comparison of input-output prediction accuracy on noisy test sets between the deep learning model and the Lindblad master equation for optical measurement of multifrequency radio signals based on Rydberg atoms^[100]

Fig. 23. Comparison of the information recovery effects between the deep learning model and the Lindblad master equation-based probe laser output spectrum processing methods when increasing the number of frequency division multiplexing channels or the frequency interval between channels to improve data transmission rate ^[100]

Table 1. Alkali atom principal quantum number (n) scaling of the most important properties of Rydberg states^[23]