1. Department of Physics and Astronomy Purdue University West Lafayette IN 47907 USA
2. Shaanxi Province Key Laboratory of Quantum Information and Quantum Optoelectronic Devices Department of Applied Physics Xi'an Jiaotong University Xi'an 710049 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