Table 6: Comparison of reversible realization of the four-bit falling-edge triggered universal register with that of the replacement design in [40] and the direct design in [26].

Quantum cost Ancilla input

Replacement design [40] 220 18
Direct design [26] 112 12
Present design 74 14
% improvement over replacement design [40] 66.36 22.22
% improvement over direct design [26] 33.93