Microwave/Terahertz communication imaging in Rydberg atoms*

Rydberg atoms are now known to have strong, narrow-band coupling to electromagnetic(EM) fields, giving rise to its use in EM calibration in the microwave (MW) and terahertz (THz) regimes. In addition, further work has been done to extract frequency, phase, and amplitude information from Rydberg atoms giving rise to the now flourishing field of atomic sensing. One such style of work was done in the usage of Rydberg atoms to image MW and THz fields with sub-wavelength resolution. To our knowledge, imaging communication protocols via Rydberg atoms have not yet been done, and as such, we present a fluorescence scheme using Rubidium as a receiver to measure communication modulations. This work is based on the fluorescence that occurs due to modulation depth and patterns of EM waves observed by the atoms. In addition, as most communication signals are coherent, we can also retrieve phase information via an additional local oscillator at the same frequency as the signal. By imaging attenuated signals in free space to replicate real-life scenarios, we anticipate thermal noise from the atmosphere and ground to mix with our signals and resolve their individual contributions. The results presented are a stepping stone to understanding the limitations of Rydberg sensors in weak field imaging. Further work can branch in two directions: adding a blue laser to create a loop detection scheme to observe the coherent emission with a heterodyne camera and lowering the power to single photon counting levels to push the boundaries of EM conversion as a possible quantum receiver.