1. Institute of Physics and University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing 100190 P. R. China
2. Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 USA
3. Faculty of Materials Science and Engineering Kunming University of Science and Technology Kunming Yunnan 650000 China
4. Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China
5. CAS Center for Excellence in Topological Quantum Computation Chinese Academy of Sciences Beijing 100190 China
6. Department of Physics University of Maryland College Park MD 20742‐4111 USA