A novel antenna gain measurement method based on quantum interaction of highly excited alkali Rydberg atoms and radiated radio frequency electric field from an antenna under test is proposed in this letter. The method allows gain value to be determined by measuring RF field induced splitting frequency of an electromagnetically induced transparency window, antenna feeding power, and finite measurement range. The antenna gain measurement for a K -band standard gain horn antenna is presented to demonstrate the measurement setup and process, and the results are consistent with conventional measurements. The method is promising due to its advantages of simplicity, accuracy, and low cost. This work is of major significance for developing atom-based RF field and antenna characterization.

We demonstrate the sensitivity enhancement of measurement of microwave electric fields by use of the full information of the complex atomic susceptibility. The transfer characteristics of both the microwave electric fields and the noise relevant to atoms, which are mapped to two quadrature components of the probe light, are systematically measured with use of a Mach-Zehnder interferometer. On the basis of the readout of the full complex atomic susceptibility, a sensitivity enhancement of 12 dB is achieved when the probe light has red detuning of 6 MHz. The results shed light on increasing the sensitivity of atomic sensors of microwave electric fields that is beyond the capability of the traditional antenna.

基于铯里德堡原子的电磁诱导透明效应, 当光与原子能级频率共振时, 其色散将剧烈变化, 吸收减弱. 此时光脉冲在原子介质中传播时, 将会出现减速. 我们在铯原子阶梯型三能级\begin{document}$S_{1/2}\rightarrow6P_{3/2}\rightarrow49D_{5/2}$\end{document}系统中, 观察到由色散曲线陡峭变化所导致的探测光脉冲减速现象, 并系统研究了耦合光强度和原子气室温度对光脉冲减慢的影响. 实验结果表明, 耦合光越弱, 延迟时间越长; 原子气室温度越高, 减速效应越明显, 与理论计算相符. 实验结果为之后进行的通过光脉冲减速效应测量微波电场提供了实验基础.

Rydberg-atom electric-field sensors have emerged as an important research direction in quantum precision measurement, owing to their intrinsic SI traceability, noninvasive measurement capability, and wide frequency tunability. However, under free-space conditions, the geometric divergence of microwaves (MWs) limits the practical detection performance of the system. In this work, we propose and experimentally demonstrate a metasurface-assisted Rydberg-atom hybrid sensor. Through introducing wavefront shaping of the incident microwave field with a metasurface (MS), electric-field enhancement in the atomic sensing region is achieved. Without altering the intrinsic sensitivity of the Rydberg-atom sensor, the equivalent sensitivity of the hybrid sensor is improved to $57.3\mathrm{nV}{\mathrm{cm}}^{-1}{\mathrm{Hz}}^{-1/2}$. This scheme provides a new route toward high-sensitivity, integrated quantum sensing of the microwave electric field.

Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6P_3/2 state when cooling lasers of the magneto-optical trap are modulated. The experiment results show that the signal to noise ratio has been improved by 32.64 dB when the modulation depth (converted to laser frequency) and frequency are optimized to 4 MHz and 6 kHz, respectively. This technique enables us to perform a highly sensitive non-destructive detection of Rydberg atoms.

Rydberg atoms enable sensitive electric-field measurements by converting field-induced changes in atomic energy levels into optically detectable signals. This work investigates four partial discharge models using Rydberg-atom sensing, a commercial ultrahigh-frequency (UHF) antenna, and a custom-built monopole antenna. The measured time-domain signals and phase-resolved partial discharge (PRPD) patterns are compared to evaluate their temporal features and phase-dependent distributions. Particular emphasis is placed on the contribution of atomic sensing to resolving low-frequency components of discharge signals, providing information complementary to conventional UHF measurements. By linking time-domain observations with PRPD characteristics, this study explores the potential of Rydberg-atom sensing to extend the spectral information available for partial discharge characterization.