1. State Key Laboratory for Mesoscopic
Physics, Department of Physics, Peking University, Beijing 100871, China
2. State Key Laboratory of Quantum
Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China
3. Nanophotonics and Metrology Laboratory, Swiss Federal Institute of Technology Lausanne (EPFL), EPFL-STI-NAM, ELG Station 11, CH-1015 Lausanne, Switzerland