Introduction

 Reversible circuits are those circuits that do not lose information and reversible computation in a system can be performed only when the system comprises of reversible gates. These circuits can generate unique output vector from each input vector, and vice versa, that is, there is a one-to-one mapping between the input and output vectors. In reversible logic circuit the number of inputs must be equal to the number of outputs. For each input pattern there must be a unique output pattern. For each output will be used only once, (that is) no fan out is allowed. The resulting   circuit must be acyclic.