1. Department of Physics and Astronomy Purdue University West Lafayette IN 47907 USA
2. Center of Quantum Technology Research School of Physics Beijing Institute of Technology Beijing 100081 China
3. School of Electrical and Computer Engineering Purdue University West Lafayette IN 47907 USA
4. Purdue Quantum Science and Engineering Institute Purdue University West Lafayette IN 47907 USA
5. Birck Nanotechnology Center Purdue University West Lafayette IN 47907 USA