Reversible logic is the emerging field of research in the 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 circuits with minimum quantum cost. The reversible decoder designed using   Fredkin   gate  with nimum 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 beareeversible 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 than the second law of thermo-dynamics guarantees that it dissipates no heat. Fan-out and Feedback are Feedbackwed in Logical Reversibility. Reversible Logic owns its applications in various fields which include Quantum Computing, Optical Computing, Nanotechnology, 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.

Keywords-Quantum Cost, Reversible Gates, Garbage Outputs, Number of Gates.