Reversible Arithmetic Logic Unit

A function is reversible if each input vector produces a unique output vector. Reversible logic is of growing importance to many future computer technologies. In this paper, the design of a reversible Arithmetic Logic Unit (ALU) is presented making use of multiplexer unit as well as control signals. ALU is one of the most important components of CPU that can be part of a programmable reversible computing device such as a quantum computer. In multiplexer based ALU the operations are performed depending on the selection line. The control unit based ALU is developed with 9n elementary reversible gates for four basic arithmetic logical operations on two n-bit operands. The series of operations are performed on the same line depending on control signals, instead of selecting the desired result by a multiplexer. The later design is found to be advantageous over the former in terms of number of garbage outputs and constant inputs produced.