Hyperfine effects in Rydberg atom-based sensing have been observed for sensing polarization. However, in most work to date, the hyperfine structure involved in the radio frequency transition has been ignored because the residual Doppler widths realized in experiments are larger than the hyperfine energy splittings of the Rydberg states. Recently, we have proposed and demonstrated a collinear three photon scheme for Rydberg atom-based electrometry that has a greatly reduced residual Doppler width, < 500 kHz. In these experiments, we observe the effect of optical pumping and the hyperfine structure of the Rydberg states. We compare the 42P3/2 → 41D5/2 and 42P3/2 → 41D3/2 sensing transitions to show that Rydberg atom hyperfine structure effects can be observed at our spectral resolution. Hyperfine structure and optical pumping can alter the effective transition dipole moments on the sensing transition and can be used to detect polarization of the radio frequency field so our work is important for practical Rydberg atom electric field sensing.
Hyperfine effects in Rydberg atom-based sensing have been observed for sensing polarization. However, in most work to date, the hyperfine structure involved in the radio frequency transition has been ignored because the residual Doppler widths realized in experiments are larger than the hyperfine energy splittings of the Rydberg states. Recently, we have proposed and demonstrated a collinear three photon scheme for Rydberg atom-based electrometry that has a greatly reduced residual Doppler width, < 500 kHz. In these experiments, we observe the effect of optical pumping and the hyperfine structure of the Rydberg states. We compare the 42P3/2 → 41D5/2 and 42P3/2 → 41D3/2 sensing transitions to show that Rydberg atom hyperfine structure effects can be observed at our spectral resolution. Hyperfine structure and optical pumping can alter the effective transition dipole moments on the sensing transition and can be used to detect polarization of the radio frequency field so our work is important for practical Rydberg atom electric field sensing.
We describe experiments relevant to Rydberg atom-based sensing. In Rydberg atom-based sensing, atoms contained in a vapor cell are used as a probe of an incident radio frequency electric field. We present a novel approach based on a collinear three-photon read-out and detection scheme, which extends the sensing range of the self-calibrated Autler-Townes sensing mode to lower electric field strengths. We demonstrate proof of concept and present concrete results from first experiments. We show that we are able to measure electric field strengths below 1 mV/cm in the self-calibrated Autler-Townes regime for a radial dipole moment of 2206 ea0for a transition at 10.7 GHz. We measure an Autler-Townes splitting of 503(6) kHz, which is equivalent to a radio frequency electric field strength of micro-V/cm.
We have shown that Rydberg atoms can be used for high-sensitivity, absolute sensing of radio frequency (RF) electric fields. We achieved a sensitivity of 3 μVcm-1Hz-1/2 for two read-out strategies. Results using a Mach-Zehnder interferometer2 and frequency modulated spectroscopy both achieve similar photon shot noise limited sensitivity. Fundamental limits to the sensitivity of the Rydberg atom-based RF electric field sensing have been addressed. Depending on the spectral resolution of the read-out, either the RF induced transmission line frequency splitting, the Autler-Townes regime, or a change in the on-resonant absorption, the amplitude regime, can be used to determine the RF electric field. Here, we present theoretical results of a 3-photon read-out scheme which enables the Autler-Townes regime of Rydberg atom-based RF electrometry to be extended to lower RF electric field strengths. We show that the residual Doppler shifts can, in principle, be reduced to ~11.8 kHz, on the order of the Rydberg atom natural lindewidths, using the approach.
In this work, we present a high-sensitivity, all-optical, atom-based radio-frequency electrometry technique, implemented via a collinear three-photon excitation scheme in a room-temperature cesium vapor cell. By employing a wave-vector matching condition unique to cesium, our approach reduces the residual Doppler broadening so that it does not dominate the electromagnetically induced absorption linewidth, achieving linewidths below 200 kHz. The narrow linewidth enables the expansion of the self-calibrated Autler-Townes sensing regime and increased sensitivity when compared to methods where Doppler broadening dominates the linewidth. In this paper, we report our latest sensitivity measurements which successfully detected radio-frequency (RF) Rabi frequencies of 2π×43 kHz using a 480 kHz measurement bandwidth at 10.7 GHz, corresponding to a sensitivity of 45 nV/cm/ √ Hz. The results of our experiment show a thirteen-fold improvement compared to our previously reported findings for all-optical atom-based electrometry. Our measurements demonstrate the ability to detect time-varying signals suitable for radar and communication applications with high sensitivity.
The Rydberg atom-based microwave electric field sensor has high sensitivity for weak RF-field detection. Selection of Rydberg states with larger electric dipole moment is beneficial to enhance the sensitivity, and we choose Rydberg states with its principal quantum number up to n ∼ 80. We study the probe laser transmission response to a microwave field for these chosen high Rydberg states at room temperature. It agrees well with theoretical simulation based on an optical Bloch equation with considered microwave-atom interaction and Doppler broadening effect. In our experiment, the microwave sensing sensitivity based on 85 Rb transition | 78 S 1 / 2 ⟩ → | 78 P 3 / 2 ⟩ arrives at 5.102(49) nV cm − 1 Hz − 1 / 2 at 1 kHz.
Rydberg atoms are neutral atoms excited to high principal quantum number states, which endows them with exaggerated properties such as large electric dipole moments, long lifetimes, and extreme sensitivity to external electromagnetic fields. These characteristics form the foundation of Rydberg atom-based sensors, an emerging class of quantum devices capable of optically detecting electric fields across frequencies from DC to the terahertz regime. Rydberg-based electrometry operates through both Autler–Townes (AT) splitting of resonant Rydberg transitions and Stark-shift measurements for high-frequency or far-detuned fields, enabling broadband field sensing from DC to the THz regime. Using ladder-type electromagnetically induced transparency (EIT) and AT splitting, these sensors enable non-invasive, SI-traceable measurements of field amplitude, frequency, phase, and polarization. Recent developments have demonstrated broadband electric field probes, voltage calibration standards, and compact RF receivers based on thermal vapor cells and integrated photonic architectures. Furthermore, innovations in multi-photon EIT, superheterodyne readout, and multi wave mixing have expanded the dynamic range and bandwidth of Rydberg-based electrometry. Despite challenges related to environmental perturbations, linewidth broadening, and laser stabilization, ongoing advances in atomic control, hybrid photonic integration, and EIT-based readout promise scalable, chip-compatible sensors. This review summarizes the physical principles, experimental progress, and emerging applications of Rydberg atom-based sensing, emphasizing their potential for next generation quantum metrology, wireless communication, and precision field mapping.
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.