  Reversible circuits have applications in digital signal processing, computer
graphics, quantum computation and cryptography. In this paper, a generalized
k*k reversible gate family is proposed and a 3*3 gate of the family is
discussed. Inverter, AND, OR, NAND, NOR, and EXOR gates can be realized by this
gate. Implementation of a full-adder circuit using two such 3*3 gates is given.
This full-adder circuit contains only two reversible gates and produces no
extra garbage outputs. The proposed full-adder circuit is efficient in terms of
gate count, garbage outputs and quantum cost. A 4-bit carry skip adder is
designed using this full-adder circuit and a variable block carry skip adder is
discussed. Necessary equations required to evaluate these adder are presented.
