We report on the development of detection methods for amplitude and phase of pulsed radio-frequency (RF) electromagnetic fields with Rydberg atoms. We begin with an overview of the basic principles of Rydberg-atom-based sensing and measurement of RF electromagnetic fields. An overview of the underlying atomic physics and the method for amplitude as well as phase sensing of electromagnetic radiation with Rydberg atoms is provided. Atomic RF receivers using Rydberg atoms for analog and digital communications and sensing of modulated RF fields are discussed. Detection of pulse-modulated RF and time-domain RF pulse waveform imaging with a Rydberg-atom receiver are demonstrated. The transient response of the Rydberg-atom vapor to a modulated RF field is observed at the 10-nanosecond level, from which a new lower limit to the achievable instantaneous signal bandwidth of atomic RF receivers is established. Finally, we present and describe a new method to measure the phase of an RF field implemented to not require an RF reference wave. The method employs phase-coherent excitation pathways involving the optical fields in the atomic sensing medium with the signal RF field. The optical RF phase-sensing approach lends itself to the realization of atomic RF sensors, measurement and imaging devices that are relevant to applications in RF communications and sensing.
We report on the development of detection methods for amplitude and phase of pulsed radio-frequency (RF) electromagnetic fields with Rydberg atoms. We begin with an overview of the basic principles of Rydberg-atom-based sensing and measurement of RF electromagnetic fields. An overview of the underlying atomic physics and the method for amplitude as well as phase sensing of electromagnetic radiation with Rydberg atoms is provided. Atomic RF receivers using Rydberg atoms for analog and digital communications and sensing of modulated RF fields are discussed. Detection of pulse-modulated RF and time-domain RF pulse waveform imaging with a Rydberg-atom receiver are demonstrated. The transient response of the Rydberg-atom vapor to a modulated RF field is observed at the 10-nanosecond level, from which a new lower limit to the achievable instantaneous signal bandwidth of atomic RF receivers is established. Finally, we present and describe a new method to measure the phase of an RF field implemented to not require an RF reference wave. The method employs phase-coherent excitation pathways involving the optical fields in the atomic sensing medium with the signal RF field. The optical RF phase-sensing approach lends itself to the realization of atomic RF sensors, measurement and imaging devices that are relevant to applications in RF communications and sensing.
With the escalating development of the quantum information technologies, the Rydberg atomic receiver has been envisioned as a promising alternative to its classical electronic counterparts, attracting extensive attentions from both physics and electronic engineering disciplines. By exploiting the electrical acuteness of Alkali atoms with diverse Rydberg energy states for electromagnetic field measurement, Rydberg atomic receiver is capable of surmounting the inherent limitations on the operating bandwidth and detection sensitivity of the classical electronic counterparts. Against this background, this article provides an extensive overview of Rydberg atomic communication and sensing from fundamental theory, critical technologies to practical implementations. Firstly, the milestones of the Rydberg atomic receiver evolution was introduced. Then we provide a clear understanding of Rydberg atomic receiver mechanisms from the perspective of classical communication and sensing, and highlight the unprecedented advantages over traditional electronic receivers as well as the technical challenges. Afterwards, necessary fundamentals are presented including the Rydberg atoms, typical non-coherent/coherent structures, and explicit experimental configurations, followed by discussions on state-of-the-art development of the Rydberg atomic receiver. Specifically, advancements on electric-field detection methods for accurate measurement of amplitude, phase, frequency and polarization, are extensively investigated. Based on the established methodologies, recent innovations in Rydberg atomic communication and sensing are reviewed, ranging from waveform design and array-based signal processing to radar applications like localization, imaging and remote sensing, with practical experimental results presented. Finally, we summarize the promising research trends around Rydberg atomic receiver.
The highly-excited Rydberg states are with a unique property of radio-frequency (RF) resonance, and Rydberg atoms at room temperature are promising for developing a broadband RF electric field sensor and relevant metrology standards. In this paper, the working mechanism of an atomic amplitude-modulation(AM) radio receiver is investigated in detail, and various factors affecting the communication quality are discussed. The modulation RF signal can be directly retrieved by measuring the transmission of a probe laser at resonance of rubidium D2 transition using a fast photo-diode detector, without any conventional demodulation process. Various communication experiments are tested at a 10.22 GHz carrier, and a modulation bandwidth of 1 MHz and an acceptable data transfer rate of about 1 Mbps have been achieved using current detection techniques. Owing to a potential high sensitivity and ultra-broadband capability of free-space RF field sensing, the quantum receiver has great significance compared with conventional electronics-based receivers, including but not limited to a weak signal, long-distance, and broadband communication in free space or via a fiber link.
Rydberg-atom-based electrometry provides a quantum, SI-traceable approach to radio-frequency (RF) and microwave electric-field sensing by linking optical spectra to absolute field strength through electromagnetically induced trans parency. Over the past decade, rapid advances in excitation schemes, field-tuning methods, interferometric readout, and cavity-assisted coupling have significantly improved sensitivity, bandwidth, and tunability of Rydberg-based sensors. In parallel, progress in fiber-coupled modules, microfabricated vapor cells, and photonic integration is enabling compact and deployable receiver architectures. This review presents a comprehensive and metrology-oriented synthesis of the physical principles, system architectures, standardized performance metrics, and uncertainty considerations relevant to Rydberg-atom RF sensing. By con solidating diverse developments into a unified performance and evaluation framework, this work provides a critical reference for the design, comparison, and advancement of next-generation quantum RF sensors and standards.
In this work, theoretical and experimental works on Rydberg-atom based radio-frequency (RF) sensors are presented. The results were obtained in close collaboration with the Quantum Valley Ideas Lab, whose goal is the miniaturization and prototyping of these sensors. The Rydberg-atom based RF sensors utilize lasers to coherently excite an atomic vapor in a vapor cell at room temperature to a highly excited Rydberg state, which is extremely sensitive to external environmental influences. In this work, Rydberg-atom based RF sensing is described as coherent multi-photon interference in the atom-light coupled system by introducing atom-light coherences. The presence of the RF wave influences the absorption of a probe laser propagating through the atomic medium. The atomic response of the Rydberg-atoms can be engineered by changing the atom-light coherences through laser power and frequency. Analytic expressions for the atomic response to the incident RF wave are derived in the weak probe limit and provide a deeper understanding of the underlying coherent multi-photon interference processes, which help to further tailor the Rydberg-atom for the purpose of the application. Good agreement with full numerical simulations of the Lindblad-master equation is found. An analysis of the various Doppler limits strongly motivates an excitation scheme where the effective wave vector mismatch on the Rydberg transition vanishes, as a promising candidate to achieve narrower spectral linewidths and, consequently, a higher sensitivity. The level structure of cesium presents a unique three-photon excitation scheme where residual Doppler shifts become comparable to the spectral linewidth of the coupling lasers. The experimental realization of this excitation scheme is demonstrated. A spectral linewidth of the Rydberg transition of 190 kHz is achieved. The measurements present the world record sensitivity, 45 nV/cm/Hz^1/2, for all-optical RF sensing with room temperature operation. These results make the three-photon excitation scheme a prime candidate for the next generation of Rydberg-atom based RF sensor prototypes. Finally, all-optical phase-sensitive RF detection is theoretically investigated in a closed-loop excitation scheme. An analytic expression is derived that intuitively describes the atomic response. Furthermore, it provides insights into the probe intensity dynamics that occur when the system is operated under finite detuning. These oscillatory dynamics allow for the extraction of the in- (I) and out- (Q) of-phase response to the RF wave, thereby enabling the simultaneous detection of the RF E-field amplitude and phase. A blueprint for the experimental realization is presented, and angle-of-arrival tolerances for the RF wave are estimated. A quadrature amplitude modulation (QAM) sequence was modelled and the simultaneous extraction of the phase and amplitude of the RF wave of interest was successfully demonstrated.
Microwave sensing offers important applications in areas such as data communication and remote sensing. It has thus received much attention from academia, industry, and governments. Atomic wireless sensing uses the strong response of the large electric dipole moment of a Rydberg atom in response to an external field to achieve precise measurement of a radio frequency (RF) signal. This method offers advantages over traditional wireless sensing including ultrawide energy level transitions, which makes it responsive to RF electric fields over a wide bandwidth. Here, we briefly review the progress of electric field measurement based on Rydberg atoms. We discuss the properties of Rydberg atoms, measurement using Rydberg atoms, experimental progress in electric field measurement of different bands, and different methods for detecting electric fields (such as atomic superheterodyne, machine learning, and critically enhanced measurement). The development of Rydberg atomic measurement focuses on the advantages of Rydberg atomic sensing, especially when compared to conventional microwave receivers. This work is of major significance to developing Rydberg-based measurements in astronomy, remote sensing, and other fields.