A new CRL gate as super class of Fredkin gate to design reversible quantum circuits

Conservative reversible logic gate is a reversible logic gate that is reversible in nature and also satisfy the property that there are equal number of 1s in the outputs as in the inputs. In this work, we present a new class of n × n (n inputs and n outputs) conservative reversible logic gate named SCRL (Super Conservative Reversible Logic) gate for the design of reversible quantum circuits. The proposed SCRL gate has 1 control input depending on the value of which it can swap any two n - 1 data inputs, hence is superior to the existing Fredkin gate. In reversible circuits, the constant input bits that are used to realize different logic functions are referred to as ancilla inputs, while the outputs that are neither primary inputs nor contribute to any useful computations are referred to as garbage outputs. As Ancilla inputs and garbage outputs are overhead bits in a reversible circuit, they need to be minimized. Barrel shifter forms an integral component of many computing systems. As an example of using the proposed SCRL gate to design efficient reversible quantum circuits, the design of reversible barrel shifter with zero ancilla inputs and zero garbage outputs is illustrated.