Optimized Reversible carry select BCD a dders using Reversible logic gates

Reversible logic is very important in construction of low power and low energy loss computational structures that are important in the construction of arithmetic circuits which are used in quantum computation and in low power digital circuits. In this paper an optimized and low quantum cost one digit carry select BCD adder using reversible logic gates is proposed. And new gate called PB gate has been proposed to get optimal result in design 2.The proposed work is best compared to existing circuits.