1. School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
2. Department of Physics, University of Fribourg, Chemin du Musée 3, 1700 Fribourg, Switzerland
3. Walker College of Business, Appalachian State University, Boone, NC 28608, USA
4. School of Mathematical Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China
5. Department of Electrical and Computer Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
6. Terry College of Business, University of Georgia, Athens, GA 30602, USA