Luminescence-based molecular scale logic circuits

We show how a half-adder logic circuit can be implemented on one molecule for a molecule exhibiting both S1→S0 and S2→S0 fluorescence. This is achieved by using both one photon S0→S1 excitation and consecutive S1→S2 excitation and establishing logic thresholds by utilizing the laser-induced photoquenching process. We present results pertaining to rhodamine and azulene molecules, in which, for the first time, an all optical half-adder logic circuit is implemented.