Over the past decades, significant progress has been made in Rydberg-atom-based electrometry. Electric field measurement with Rydberg atoms features high sensitivity and self-calibration. It has proven to be an excellent quantum receiver for microwave communications. The Rydberg atomic receiver has several advantages: the non-metallic atomic probe does not interfere with the field to be measured, and non-destructive communication can be achieved. The Rydberg atomic sensor converts high-frequency microwaves into spectral detection; thereby, the microwave electric field modulation is directly mapped to the atomic spectrum. Therefore, the all-optical detection scheme makes the atomic receiver demodulation circuit-free and immune to electromagnetic interference. Moreover, the operational bandwidth of the Rydberg atomic receiver can span from MHz to THz by selecting different Rydberg energy levels. Last but not least, the instantaneous bandwidth of the Rydberg atomic receiver is not limited by the size of the antenna, because the Rydberg atomic receiver breaks a key assumption behind the Chu limit.

Significant advances have been achieved in Rydberg atomic receivers. This paper provides a comprehensive overview of advancement in Rydberg atomic-based communication receivers. The Rydberg atomic-based communication receivers are systematically classified into three main categories: single-channel Rydberg atomic receivers, frequency-division multiplexing (FDM) receivers, and multiple-input multiple-output (MIMO) multiplexing communication receivers. For the single-channel Rydberg atomic receivers, researchers have successfully realized both analog and digital communications by using amplitude modulation, frequency modulation, and phase modulation schemes within Rydberg atomic receiver systems. Meanwhile, the instantaneous bandwidth of the Rydberg atomic receivers and its emerging applications in 5G wireless communication is explored. The shortcoming of Rydberg atomic receivers is mainly reflected in insufficient instantaneous bandwidth (~10 MHz), which limits the channel capacity of the receiver system. To enhance the channel capacity, frequency-division multiplexing (FDM) and multiple-input multiple-output (MIMO) communications based on Rydberg atomic receivers have been investigated and demonstrated. As for frequency-division multiplexing (FDM) based on Rydberg atomic receivers, both standard FDM and multi-band FDM Rydberg atom receiver schemes and progresses are presented. Last but not least, the MIMO-based multiplexing scheme is also introduced to enhance spectral efficiency and system capacity. The above-mentioned achievements have laid the foundation for the future integration of Rydberg atomic receiver technology into existing 5G wireless communication systems.

The future development of Rydberg atomic receivers focus on the following four aspects. First, in the transmission model of a Rydberg atom receiver, it is necessary to consider not only the interaction between Rydberg atoms and microwave fields but also the Rydberg-Rydberg interaction, which also influences the dynamics of quantum states. Secondly, in the frequency-division multiplexing communication system, the master equation of the Rydberg atom system becomes complex and difficult to solve. In the future, deep learning models may provide effective solutions for understanding and optimizing Rydberg atomic receiver systems. Third, all-optical Rydberg atomic receivers offer excellent scalability; therefore, multiple-input multiple-output (MIMO) Rydberg atom receiver system is promising. Finally, Rydberg atomic communication receivers are expected to be integrated into existing wireless communication systems, improving the communication range of wireless communications.