[Ling, Xiaohui] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.^[Zhou, Xinxing] Hunan Normal Univ, Synerget Innovat Ctr Quantum Effects & Applicat, Coll Phys & Informat Sci, Changsha 410081, Hunan, Peoples R China.^[Qiu, Cheng-Wei] Natl Univ Singapore, Dept Elect & Comp Engn, 4 Engn Dr 3, Singapore 117576, Singapore.