An Efficient Design of Reversible Multi-Bit Quantum Comparator Via Only a Single Ancillary Bit

Quantum computing has emerged as one of the most promising technology due to its powerful computing capability. And quantum basic circuits like quantum comparator, quantum adder etc, are the foundation to realize quantum computing. In this paper, we present an efficient design to realize the comparison of two n-bit quantum logic states via only a single ancillary bit. Our proposed comparator compares two n-bit quantum logic states and identifies which of them is the largest, which of them is the smallest, and which of them is equal in linear quantum depth. Moreover, we analyze the superior performance of our proposed comparator in terms of auxiliary bits compared with the existing quantum logic comparators.