Subwavelength micromachined vapor-cell-based Rydberg quantum antennas

Micromachined vapor cells have revolutionized chip-scale quantum sensors, including magnetometers and atomic clocks. In parallel, Rydberg-atom quantum sensing has emerged as a powerful platform for broadband, non-invasive and ultra-sensitive electrometry, enabling compact atom-based antenna elements for electromagnetic reception, often referred to as quantum antennas. Yet, to date, Rydberg sensing has largely been limited to glass-blown, cm-scale vapor cells. Here, we perform Rydberg spectroscopy and electrometry using a wafer-scale-fabricated Pyrex–Si–Pyrex cell with millimeter-scale dimensions. The Rydberg spectroscopic line is characterized with respect to critical parameters such as temperature, the frequency and amplitude of the applied radio frequency (RF) field, light intensity, and the spatial position of the interrogating beam. Our study reveals lineshapes directly influenced by a complex landscape of electrostatic fields with values up to approximately 0.6 V cm (Formula presented) (Formula presented). By controlling key parameters, we were able to reduce the effect of these internal electric fields, and demonstrate the detection of RF fields assessed using the Autler–Townes splitting with a minimum detectable field of 20 (Formula presented) (Formula presented) V cm (Formula presented) (Formula presented). Our results highlight the potential of micromachined vapor cells for subwavelength electromagnetic field measurements, with applications in communications, near-field RF imaging, and chip-scale quantum technologies.