Rydberg Atoms for Radio-Frequency Communications and Sensing: Atomic Receivers for Pulsed RF Field and Phase Detection

We report on the development of detection methods for amplitude and phase of pulsed radio-frequency (RF) electromagnetic fields with Rydberg atoms. We begin with an overview of the basic principles of Rydberg-atom-based sensing and measurement of RF electromagnetic fields. An overview of the underlying atomic physics and the method for amplitude as well as phase sensing of electromagnetic radiation with Rydberg atoms is provided. Atomic RF receivers using Rydberg atoms for analog and digital communications and sensing of modulated RF fields are discussed. Detection of pulse-modulated RF and time-domain RF pulse waveform imaging with a Rydberg-atom receiver are demonstrated. The transient response of the Rydberg-atom vapor to a modulated RF field is observed at the 10-nanosecond level, from which a new lower limit to the achievable instantaneous signal bandwidth of atomic RF receivers is established. Finally, we present and describe a new method to measure the phase of an RF field implemented to not require an RF reference wave. The method employs phase-coherent excitation pathways involving the optical fields in the atomic sensing medium with the signal RF field. The optical RF phase-sensing approach lends itself to the realization of atomic RF sensors, measurement and imaging devices that are relevant to applications in RF communications and sensing.