Atom-Based Sensing of Weak Radio Frequency Electric Fields Using Homodyne Readout

TL;DR

This paper demonstrates a highly sensitive atom-based radio-frequency electric field sensor using homodyne detection, achieving a new sensitivity limit and analyzing dephasing mechanisms affecting performance.

Contribution

It introduces a homodyne detection method with a Mach-Zehnder interferometer for atom-based RF electric field sensing, reaching unprecedented sensitivity levels.

Findings

Achieved sensitivity of 5 μV/cm/Hz^{1/2} in RF electric field sensing.

Identified photon shot noise as the current limiting factor.

Compared experimental results with density matrix calculations.

Abstract

We utilize a homodyne detection technique to achieve a new sensitivity limit for atom-based, absolute radio-frequency electric field sensing of $\mathrm{5 \mu V cm^{-1} Hz^{-1/2} }$. A Mach-Zehnder interferometer is used for the homodyne detection. With the increased sensitivity, we investigate the dominant dephasing mechanisms that affect the performance of the sensor. In particular, we present data on power broadening, collisional broadening and transit time broadening. Our results are compared to density matrix calculations. We show that photon shot noise in the signal readout is currently a limiting factor. We suggest that new approaches with superior readout with respect to photon shot noise are needed to increase the sensitivity further.