Guo Guangcan's team at CSU realizes Reedeburg Atomic Microwave Frequency Comb Spectrometer

Academician Guo Guangcan's team at the Chinese University of Science and Technology (CSU) has made new progress in wireless sensing based on Reedeburg atoms. The group of Shi Baosen and Ding Dongsheng realized a Rydberg atom-based microwave frequency comb spectrometer, which has promising applications in the field of broadband microwave detection.

The related results were published in the journal Physical Review Applications on July 14 under the title "Rydberg microwave frequency comb spectrometer".

Microwave measurements play an important role in communications, navigation, radar, and astronomical detection. The Rydberg atom has a large electric dipole moment, and it can have a strong response to weak electric fields, so the Rydberg atom can be used as a microwave sensor. In recent years, this research direction has received a lot of attention, e.g., David H. Meyer et al. of the U.S. Army Research Office demonstrated an atomic RF receiver and spectrum analyzer based on a thermal Reedeburg atom coupled to a planar microwave waveguide [Physical Review Applied 15, 014047 (2021)]. Despite the important progress in Riedberg atomic sensing research, there are still some pressing problems, such as the bandwidth of the signal that can be received in real time (instantaneous bandwidth) is limited by the relaxation time of the atomic system to reach the steady state, which is usually only a few MHz, which seriously affects the practicalization of this system.

In this work, the research team has demonstrated an absolute microwave frequency measurement scheme based on the Reedeburg microwave frequency comb spectrometer based on the room temperature cesium atomic system, using the mixing response property of Reedeburg atoms to microwaves, and setting the microwave frequency comb signal as the local oscillation signal (as shown in Fig. 1), with the current achievable real-time response range of 125 MHz and room for further improvement. In addition, as shown in Fig. 2, the system achieves the reception of signals with 1 kHz modulation bandwidth at different center frequencies by using Riedberg states with different principal quantum numbers.

Fig. 1 (a) Diagram of the atomic energy level. (b) Schematic diagram of the absolute frequency measurement (c) Diagram of the experimental setup

Fig. 2 Demonstration of the reception of different Riedberg states (with different principal quantum numbers n) for 1 kHz bandwidth modulated signals with different center frequencies.

The innovation of this work is to use microwave frequency combs to broaden the response range of Riedberg atoms to microwave signals, which to some extent compensates for the narrow transient bandwidth of Riedberg atoms in microwave detection and enables absolute frequency measurement of signals in a wider range, which can fully exploit the large response bandwidth and high sensitivity of Riedberg atoms to microwaves. In addition, the method can also effectively receive phase information, which is expected to be applied to microwave communication and measurement, etc.

Hua Zhang, a PhD student at the Key Laboratory of Quantum Information, CAS, is the first author of this paper, and Prof. Dongsheng Ding and Prof. Baoshen Shi are the co-corresponding authors. The results were supported by the Ministry of Science and Technology, the Foundation Committee, the Chinese Academy of Sciences, the Major Science and Technology Project of Anhui Province, and the University of Science and Technology of China.

Article Links：

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.18.014033