A quantum-based power standard: Using Rydberg atoms for a SI-traceable radio-frequency power measurement technique in rectangular waveguides

In this work, we demonstrate an approach for determining radio-frequency (RF) power using electromagnetically induced transparency (EIT) in a Rydberg atomic vapor. This is accomplished by placing alkali atomic vapor in a rectangular waveguide and measuring the electric (E) field strength (utilizing EIT and Autler-Townes splitting) for a wave propagating down the waveguide. The RF power carried by the wave is then related to this measured E-field, which leads to a direct International System of Units measurement of RF power. To demonstrate this approach, we first measure the field distribution of the fundamental mode in the waveguide and then determine the power carried by the wave at both 19.629 GHz and 26.526 GHz from the measured E-field. We show comparisons between the RF power obtained with this technique and those obtained with a conventional power meter.