1. Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan 430074 China
2. Department of Electrical and Computer Engineering National University of Singapore 4 Engineering Drive 3 117583 Singapore
3. Institute of Microelectronics Agency for Science, Technology and Research (A*STAR) 2 Fusionopolis Way 138634 Singapore
4. Quantum Science and Engineering Centre (QSec) Nanyang Technological University 50 Nanyang Ave 639798 Singapore