Highly excited Rydberg atoms in a room-temperature vapor cell are promising for developing a radio-frequency (RF) electric field (E-field) sensor and relevant measurement standards with high accuracy and sensitivity. The all-optical sensing approach is based on electromagnetically-induced transparency and Autler-Townes splitting induced by the RF E-field. Systematic investigation of measurement uncertainty is of great importance for developing a national measurement standard. The presence of a dielectric vapor cell containing alkali atoms changes the magnitude, polarization, and spatial distribution of the incident RF field. In this paper, the field distortion of rubidium vapor cells is investigated, in terms of both field strength distortion and depolarization. Full-wave numerical simulation and analysis are employed to determine general optimization solutions for minimizing such distortion and validated by measuring the E-field vector distribution inside different vapor cells. This work can improve the accuracy of atom-based RF E-field measurements and contributes to the development of related RF quantum sensors.

Herein, a microfabricated millimeter-level vapor alkali cell with a high hermeticity is fabricated through a wet etching and single-chip anodic bonding process. The vapor cell, containing Rb and N₂, was investigated in a coherent population trapping (CPT) setup for the application of a chip-scale atomic clock (CSAC). The contrast of CPT resonance is up to 1.1% within the only 1 mm length of light interacting with atom. The effects of some critical external parameters on the CPT resonance, such as laser intensity, cell temperature, and buffer gas pressure, are thoroughly studied and optimized. The improved microfabricated vapor cell also exhibited great potential for other chip-scale atomic devices.

We present a coherent population trapping clock system based on laser-cooled ⁸⁷Rb atoms. The clock consists of a frequency-stabilized CPT interrogation laser and a cooling laser as well as a compact magneto-optical trap, a high-performance microwave synthesizer, and a signal detection system. The resonance signal in the continuous wave regime exhibits an absorption contrast of ∼ 50%. In the Ramsey interrogation method, the linewidth of the central fringe is 31.25 Hz. The system achieves fractional frequency stability of 2.4 × 10 − 11 / τ , which goes down to 1.8 × 10⁻¹³ at 20000 s. The results validate that cold atom interrogation can improve the long-term frequency stability of coherent population trapping clocks and holds the potential for developing compact/miniature cold atoms clocks.

Australia's national citizen science program VegeSafe has collected and analysed over 26,000 residential garden soil samples for their trace metal concentrations, enabling a more comprehensive understanding of the factors influencing contamination. Here we analysed spatial data from 8221 soil samples collected from 1828 homes across Greater Sydney, Australia's largest city, using an optimal parameter-based geographical detector (OPGD) model to quantify anthropogenic and natural factors influencing urban residential soil trace metal concentrations. The OPGD model identifies optimal spatial scales and discretization parameters, enhancing spatial stratified heterogeneity analysis. Results demonstrate anthropogenic factors, such as aged/painted home density, road density, and industrial trace metal emissions, primarily contribute to soil concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn). By contrast, natural factors including soil pH, regolith stability, and soil type dominate soil manganese (Mn) and nickel (Ni) concentrations. Strongest interactive effects typically involve an anthropogenic and a natural factor. Notably, 42.7 % of homes within the study area had at least one soil sample with Pb concentrations exceeding the Australian residential guideline of 300 mg/kg. Locations with potential risk of harm are identified to inform targeted mitigation strategies. Compared to machine learning methods, the OPGD model offers a more reliable and comprehensive assessment of urban residential soil trace metal contamination.

A microwave (MW) synthesizer is a key component of high-performance coherent population trapping (CPT) atomic clocks, which are competitive candidates as miniature, low-power-consumption atomic clocks. In this work, we demonstrated a microwave synthesizer and a self-adaption system to satisfy the requirement of short term and mid-long term frequency stability of CPT clocks. From the experimental results, the absolute phase noise of the microwave synthesizer was measured as -110 dBc/Hz at 200 Hz. The off-resonant light shift limitation for CPT clock can achieve better than 1×10-14 based on our microwave synthesizer and self-adaption system. The proposed low-phase-noise microwave synthesizer and self-adaption system presented can also be used in other high-performance microwave atomic sensors and standards.

As an important “tool” in microwave science and engineering, quantum sensing techniques have been studied in a broad range of fields such as microwave electrometry, microwave magnetic field detection. In this work, we measured the relaxation rate of Rb vapor cell with Rabi resonance-based quantum sensing technique in a microwave cavity. The characterization of Rabi resonance lineshape with different experimental parameters are investigated. The relaxation rate of the vapor cell could be obtained by the Rabi resonance lineshape.