1. Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China
2. Synergetic Innovation
Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
3. Physics Department, The University of Michigan, Ann
Arbor, Michigan 48109-1040, United States
4. Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, California 90095, United States