Determining the angle-of-arrival of a radio-frequency source with a Rydberg atom-based sensor

In this work, we demonstrate the use of a Rydberg atom-based sensor for determining angle arrival an incident radio frequency (RF) wave or signal. The technique uses electromagnetically induced transparency in atomic vapor conjunction with heterodyne mixer. atom mixer measures phase RF at two different locations inside cell. difference these is related to direction wave. To approach, measure differences 19.18 GHz cell filled cesium atoms various angles. Comparisons measurements both full-wave simulation and plane theoretical model show that sub-wavelength can be used determine field.