ECAMP 15

In the past decade, Rydberg atoms have emerged as promising and valuable tools for a myriad of quantum applications, and particularly quantum sensors. The exaggerated properties of Rydberg atoms make them highly sensitive to electric fields spanning from DC to THz frequencies, which makes them an appealing tool for sensitive, accurate, and simple sensors. This field is of tremendous interest to a wide range of industries, particularly electric field sensing. Indeed, much work has been done showcasing sensitive, accurate and cost-effective atomic Rydberg sensors. While numerous demonstrations have realized such sensors using centimeter-scale vapor cells [1,2], efforts to miniaturize Rydberg-based field sensors to millimeter footprints remain scarce.
Leveraging advances in wafer-scale microfabrication—which have already transformed chip-scale atomic clocks and magnetometers [3]—we present an all-optical, sub-wavelength radio-frequency (RF) sensor based on micromachined rubidium vapor cells with millimeter-scale dimensions (Fig. 1b). We systematically investigate how proximity-induced electrostatic fields influence the Rydberg lineshape by varying cell temperature, laser power, atomic density, and beam position.
Rydberg excitation is achieved via electromagnetically induced transparency (EIT) using counter-propagating 780 nm (probe) and 480 nm (pump) lasers to access the 52D₅/₂ state (Fig. 1a). Figure 1b shows a representative EIT lineshape obtained in a 1.4 mm cell. We then apply an RF field at 15.09 GHz (52D₅/₂→51P₃/₂ transition) via an antenna ≈15 cm from the cell, inducing Autler–Townes splitting that enables direct RF amplitude measurements (Fig. 1c).
We observe clear Autler–Townes doublets whose splitting scales with the applied RF amplitude. Beyond the expected monotonic increase in linewidth and contrast, we report lineshape shifts, broadening, and asymmetry as temperature and pump power increase—signatures of DC Stark shifts arising from static fields. We attribute these fields to photoionization-induced charges on the cell walls and thermally activated surface charging. Spatially resolved measurements further reveal a nonuniform electrostatic-field profile within the cell.
Finally, the RF resonance exhibits an ≈20 MHz redshift relative to its calculated value. By incorporating DC-Stark shifts and inhomogeneous broadening into our EIT simulations, we estimate a ~0.2 V/cm DC field. This modeling informs optimized spectroscopic conditions, substantially improving signal-to-noise performance (Fig. 1c).

https://photos.app.goo.gl/N6UVEc42WqP8ekaKA

In summary, we demonstrate Rydberg-based electrometry in millimeter-scale, wafer-fabricated vapor cells that enable broadband, ultra-sensitive, non-invasive sub-wavelength RF field detection [4[. We characterize the EIT lineshape under varying electrostatic conditions at the cell windows, identify how surface charging and temperature-induced effects impact sensor performance, and introduce mitigation strategies to preserve spectroscopic fidelity. These results chart a clear pathway toward fully integrated, chip-scale Rydberg electric-field sensors with sub-wavelength resolution.

[1] Simons, Matthew T., et al. "A Rydberg atom-based mixer: Measuring the phase of a radio frequency wave." Applied Physics Letters 114.11 (2019).‏
[2] A. Duspayev, R. Cardman, D. A. Anderson, and G. Raithel, “High-angular-momentum rydberg states in a room-temperature vapor cell for dc electric-field sensing,” Phys. Rev. Res. 6, 023138 (2024).
[3] Kitching, John. "Chip-scale atomic devices." Applied Physics Reviews 5.3 (2018).‏
[4] Giat, Avital, et al. "Subwavelength micromachined vapor-cell based Rydberg sensing." arXiv preprint arXiv:2504.09559 (2025).