I. Introduction
By exploiting unique physical characteristics such quantum superposition and entanglement, quantum computer had potential to provide extraordinary computing power far exceeding classical computer, which could provide unprecedented solutions for artificial intelligence, cryptanalysis, quantitative finance, chemical simulation, drug design, etc. In recent years, quantum computing research has developed rapidly and remarkable breakthroughs have been made in several kinds of prototypes and simulators. Through the cloud platform, the entry-level quantum computing services based on quantum backends and simulators become available and popular.