1. Key Laboratory of Quantum Information, Chinese Academy of Sciences, University of Science and Technology of China, Hefei 230026, People's Republic of China
2. Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
3. Center for Micro and Nanoscale Research and Fabrication, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China