Reversible logic is the emerging field for research in present era. The aim of this paper is to realize different types of combinational circuits like full-adder, full-subtractor, multiplexer and comparator using reversible decoder circuit with minimum quantum cost. Reversible decoder
is designed using Fredkin gates with minimum Quantum cost. There are many reversible logic gates like Fredkin Gate, Feynman Gate, Double Feynman Gate, Peres Gate, Seynman Gate and many more. Reversible logic is defined as the logic in which the number output lines are equal to the number of
input lines i.e., the n-input and k-output Boolean function F(X1,X2,X3, ...,Xn) (referred to as (n,k) function) is said to be reversible if and only if (i) n is equal to k and (ii) each input pattern is mapped uniquely to output pattern.
The gate must run forward and backward that is the inputs can also be retrieved from outputs. When the device obeys these two conditions then the second law of thermo-dynamics guarantees that it dissipates no heat. Fan-out and Feed-back are not allowed in Logical Reversibility. Reversible
Logic owns its applications in various fields which include Quantum Computing, Optical Computing, Nano-technology, Computer Graphics, low power VLSI etc. Reversible logic is gaining its own importance in recent years largely due to its property of low power consumption. The comparative study
in terms of garbage outputs, Quantum Cost, numbers of gates are also presented. The Circuit has been implemented and simulated using Tannaer tools v15.0 software.