Highly sensitive measurement of a megahertz rf electric field with a Rydberg-atom sensor

TL;DR

This paper demonstrates a highly sensitive method for measuring weak MHz electric fields using Rydberg atoms and electromagnetically induced transparency, achieving record sensitivity and fidelity in a thermal atomic system.

Contribution

It introduces a heterodyne detection technique with Rydberg atoms to significantly improve sensitivity for weak MHz electric field measurements.

Findings

Minimum electric field strength measured: 37.3 μV/cm

Sensitivity achieved: -65 dBm/Hz

Fidelity of demodulated AM signal: over 98%

Abstract

Rydberg atoms have great potential in electric field measurement and have an advantage with a large frequency bandwidth from the kHz to the THz scale. However, the sensitivity for measuring a weak MHz electric field signal is limited by the spectroscopic resolution, because the weak electric field induces only a small perturbation of the population and energy level shift of the Rydberg atoms. Here, we report highly sensitive measurement of a weak MHz electric field using electromagnetically induced transparency with Rydberg atoms in a thermal atomic system. Using the heterodyne method on a 30-MHz electric field, we successfully measure the minimum electric field strength to be \textcolor{black}{37.3 $\mathrm{\mu V/cm}$} with a sensitivity up to $-65$ dBm/Hz and a linear dynamic range over 65 dB. Additionally, we measure an amplitude-modulated signal and demodulate the signal with a fidelity over 98\%. This work extends the sensitivity of atomic sensors for measuring MHz electric fields, which advances atomic electric field-sensing technology.