1. Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, California90095, United States
2. Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California90095, United States
3. Department of Physics, Harvard University, Cambridge, Massachusetts02138, United States
4. Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts02138, United States
5. Center for Quantum Science and Engineering, University of California, Los Angeles, California90095, United States
6. Challenge Institute for Quantum Computation, University of California, Los Angeles, California90095, United States