1. Department of Electronic
and Information Engineering, The Hong Kong Polytechnic University, Hong Kong, P.R. China
2. Department of Physics, Hong Kong Baptist University, Hong Kong, P.R. China
3. Department of Physics, University of Hong Kong, Hong Kong, P.R. China
4. Hefei National
Laboratory of Physical Sciences at the Microscale, Synergetic Innovation
Center of Quantum Information and Quantum Physics, CAS Key Laboratory
of Materials for Energy Conversion, and Department of Materials Science
and Engineering, University of Science and Technology of China, Hefei, Anhui 230000, P.R. China