Waveguide-Coupled Rydberg Spectrum Analyzer covering 0 to 20 GHz

We present a wideband RF receiver based on thermal Rydberg atoms coupled to the near field of a coplanar waveguide. We use this quantum sensor to perform spectrum analysis continuously from DC to 20 GHz with 4 MHz instantaneous bandwidth, 80 dB of linear dynamic range, and an intrinsic sensitivity of up to -120 dBm/Hz (improved to -145dBm/Hz with preamplification). Using this system as the backend of a standard rabbit-ears antenna, we directly measure ambient, real-world signals, including AM/FM radio as well as Wi-Fi and Bluetooth digital packets. We also demonstrate waveguide-readout of the thermal Rydberg ensemble via resonant, nondestructive RF probing. This work opens a path toward small, thermal ensemble Rydberg sensors that can surpass fundamental limitations to standard RF sensors and analyzers.