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.