Optical Measurements of Strong Microwave Fields with Rydberg Atoms in a Vapor Cell

Even in this day and age, precise absolute measurement of electric fields is not trivial. The authors extend quantum sensing via cold atoms and electromagnetically induced transparency to the strong-field regime. In this regime, existing techniques are insufficient due to the complex and highly nonlinear response of the atoms. This is an essential step toward calibration-free rf electric-field sensors for a wide range of applications that include antenna calibration, metamaterial characterization, and subwavelength imaging.