Digital terahertz communication with Rydberg-atom-based coherent photon conversion

We experimentally demonstrate digital communications in the terahertz (THz) band using a rubidium vapor cell as a quantum receiver. We utilize amplitude modulation to encode digital information in THz photons, which are coherently upconverted to optical photons via a Rydberg six-wave-mixing process. We achieve a data transmission rate of up to 1.16 Mbit/s and a tunable bandwidth of up to 142 MHz near a 0.11 THz carrier. With reduced data rate and increased integration time per bit, we demonstrate weak-field THz transmission with a receiver sensitivity in the −130 dBm range. As a proof of principle, we perform an end-to-end transmission of digital color images in the THz band. Our work provides the possibility of THz communication at the single-photon level.