1. Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
2. Laboratory for Physical Sciences, University of Maryland, College Park, Maryland 20740, USA
3. Department of Electrical and Computer Engineering and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
4. Joint Quantum Institute, University of Maryland and the National Institute of Standards and Technology, College Park, Maryland 20742, USA