1. Department of Electrical and Computer Engineering University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA
2. Department of Physics Chungbuk National University Cheongju Chungbuk 28644 South Korea
3. Interdisciplinary Center for Quantum Information State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China
4. Department of Pharmacology University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA
5. Materials Science and Engineering Program University of California San Diego 9500 Gilman Drive La Jolla CA 92093 USA