Microwave electrometry with Rydberg atoms in a vapor cell using microwave amplitude modulation

TL;DR

This paper demonstrates a method using Rydberg atom EIT-AT spectra with microwave amplitude modulation to detect extremely weak microwave fields, significantly enhancing measurement sensitivity.

Contribution

The study introduces a novel dispersive signal analysis technique that improves the detection limit of weak microwave fields using vapor cell Rydberg atoms.

Findings

Minimum detectable microwave field strength is about 30 times lower than traditional methods.

The method achieves a minimum measurable field of 0.056 mV/cm at 9.2 GHz.

The approach enhances the sensitivity of microwave electrometry without auxiliary fields.

Abstract

We have theoretically and experimentally studied the dispersive signal of the Rydberg atomic electromagnetically induced transparency (EIT) - Autler-Townes (AT) splitting spectra obtained using amplitude modulation of the microwave (MW) field. In addition to the two zero-crossing points, the dispersion signal has two positive maxima with an interval defined as the shoulder interval of the dispersion signal $\Delta f_{\text{sho}}$. The relationship of MW field strength $E_{\text{MW}}$ and $\Delta f_{\text{sho}}$ are studied at the MW frequencies of 31.6 GHz, 22.1 GHz, and 9.2 GHz respectively. The results show that $\Delta f_{\text{sho}}$ can be used to character the much weaker $E_{\text{MW}}$ than the interval of two zero-crossing points $\Delta f_{\text{zeros}}$ and the traditional EIT-AT splitting interval $\Delta f_{\text{m}}$, the minimum $E_{\text{MW}}$ measured by $\Delta f_{\text{sho}}$ is about 30 times smaller than that by $\Delta f_{\text{m}}$. As an example, the minimum $E_{\text{MW}}$ at 9.2 GHz that can be characterized by $\Delta f_{\text{sho}}$ is 0.056 mV/cm, which is the minimum value characterized by frequency interval using vapour cell without adding any auxiliary fields. The proposed method can improve the weak limit and sensitivity of $E_{\text{MW}}$ measured by spectral frequency interval, which is important in the direct measurement of weak $E_{\text{MW}}$.