[1] Univ Elect Sci & Technol China, Web Sci Ctr, Sch Comp Sci & Engn, Chengdu 610054, Peoples R China
[2] Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Peoples R China
[3] Shanghai Univ Sci & Technol, Res Ctr Complex Syst Sci, Shanghai 200093, Peoples R China
[4] Univ Fribourg, Dept Phys, CH-1700 Fribourg, Switzerland