1. Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
2. Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, P.R. China
3. Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China