1. State Key Laboratory for Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 P. R. China
2. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory Chinese Academy of Sciences Hefei Anhui 230031 P. R. China
4. Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China Hefei Anhui 230026 P. R. China
5. Beijing Academy of Quantum Information Sciences Beijing 100193 P. R. China
6. Center for Excellence in Topological Quantum Computation University of Chinese Academy of Science Beijing 100049 P. R. China