Literature survey

A gate that implements any bijective function involving n inputs and n outputs is called an n*n reversible logic gate. There exist many reversible gates in the literature. Among them 2*2 Feynman gate,3*3 Fredkin gate,3*3 Tofolli gate,3*3 Peres gate are the most referred [5,10]. Feynman (FG), Fredkin (FRG) and Peres (PG) gates are one through gates, that is, one of its output lines is identical to one of its input lines. On the other hand, Tofolli gate is two through, that is, two of its outputs are identical to two of its inputs. It can be easily verified that all of these gates are reversible. Each gate has an equal number of input and output lines. For each input combination there is a unique output combination.