1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore637371, Singapore
2. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore637371, Singapore
3. State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing100084, People’s Republic of China
4. SEU-FEI Nano-Pico Center, Key Laboratory of MEMS of Ministry of Education, Collaborative Innovation Center for Micro/Nano Fabrication, Device and System, Southeast University, Nanjing210096, People’s Republic of China
5. School of Materials Science and Engineering, Nanyang Technological University, Singapore639798, Singapore
6. Frontier Science Center for Quantum Information, Beijing100084, People’s Republic of China
7. Collaborative Innovation Center of Quantum Matter, Beijing100871, People’s Republic of China
8. Beijing Academy of Quantum Information Sciences, Beijing100193, P.R. China