1Computer Network Information Center, Chinese Academy of Sciences, Beijing 100190, China
2University of Chinese Academy of Sciences, Beijing 100049, China
3Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4Beijing University of Posts and Telecommunications, Beijing 100876, China
5New Jersey Institute of Technology, Newark, New Jersey 07102, USA
6Key Laboratory for Quantum Optics and Center for Cold Atom Physics of CAS, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
7Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
8Nokia Bell Labs, Murray Hill, New Jersey 07974, USA