[1] Dalian Univ Technol, Sch Phys & Optoelect Technol, Dalian 116024, Peoples R China
[2] Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore
[3] Natl Univ Singapore, Dept Phys, Singapore 117543, Singapore
[4] Univ Sci & Technol China, Hefei Natl Lab Phys Sci Microscale, Hefei 230026, Anhui, Peoples R China
[5] Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Anhui, Peoples R China