Fuzzy Logic in Molecular Computing

There exists a worldwide race to make microprocessors of computers as much powerful as possible by shrinking electronic components and cramming logic gates onto smaller and smaller wafers of silicon. Over the past few years, some companies and several academic laboratories have started seriously entertaining the idea of constructing computers in which computations are performed by individual molecules. If the logic gates, sculpted from bulk semiconductors, are based exclusively on electrical signals, those based on single molecules can be extended to chemical, optical and other physical inputs and outputs. Purpose of the chemist is to find out always-new powerful molecular systems that can carry out the logic operations required for computer circuitry. If the compound behaves as a versatile molecular switch, it can be adopted to process Boolean binary logic. On the other hand, if a chemical species responds to external inputs with a continuously variable output signal and the relation between inputs and output can be rationalized in terms of IF-THEN statements, it can be employed to process Fuzzy logic. Organic compounds exhibiting "Proximity Effect" in their photophysics give an opportunity to implement Fuzzy logic Engines at the molecular level. For these chemical species a quantum state, consisting of a superposition of two electronic levels, can be produced through excitation by UV-Visible radiation. The nature of the quantum state and its ability to emit light can be varied in a continuous manner by regulating environmental conditions such as temperature and hydrogen bonding donation ability of the solvent. This opens up a new avenue to implement Fuzzy logic at the molecular level.