This Chapter is concerned with quantum duality or multiplicity of states, in a molecular logic-based computing context. Nuclear magnetic resonance spectroscopy is one approach where the quantum nature of information bits comes to the fore by displaying superposition. On the other hand, electronic absorption and emission spectroscopy (as well as Raman spectroscopy) allows the quantum nature of the device to emerge. Here, we find the device can exist in multiple logic configurations at once. Molecules displaying internal charge transfer (ICT), electronic energy transfer (EET) or excimer/exciplex phenomena are very suitable substrates for these optical spectroscopic experiments.