[1] Chinese Acad Sci, Inst Semicond, Natl Lab Superlattics & Microstruct, Beijing 100083, Peoples R China
[2] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China
[3] Tsinghua Univ, Dept Math, Beijing 100084, Peoples R China
[4] Key Lab Quantum Informat & Measurements, Minist Educ, Beijing 100084, Peoples R China
[5] Tsinghua Univ, Ctr Atom Mol & Nanosci, Beijing 100084, Peoples R China