[1] Nanjing Univ, Natl Lab Solid State Microstruct, Sch Phys, Sch Engn & Appl Sci, Nanjing 210093, Jiangsu, Peoples R China
[2] Univ Calgary, Inst Quantum Informat Sci, Calgary, AB T2N 1N4, Canada
[3] Univ Arkansas, Dept Phys, Fayetteville, AR 72701 USA