1. Virginia Tech National Security Institute, Blacksburg, Virginia 24060, USA
2. Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
3. Virginia Tech Center for Quantum Information Science and Engineering, Blacksburg, Virginia 24061, USA
4. Department of Physics, University of California, Davis, California 95616, USA
5. National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China