An excitonic device comprises an exciton transmission line comprised of a row of molecules. Propagation of excitons is mediated by an exciton exchange interaction. The gate consists of a molecule “a” that interacts with a proximal molecule via a two-body exciton interaction. If the gate molecule is not excited, it does not couple to the transmission line thereby allowing incoming signals to propagate unimpeded. If the gate molecule is excited, signals are back scattered as a result of the two-body interaction between the exciton residing on “a” and the excitons on the transmission line. The ballistic exciton transistor has industrial applications that extend to at least fast optical switching, optical communication, exciton devices, and exciton-based information processing.