1. Department of Applied Physics, Stanford University 1 , Stanford, California 94305, USA
2. Department of Mechanical Engineering, and Institute for Physical Science and Technology (IPST), University of Maryland 2 , College Park, Maryland 20742, USA
3. National Quantum Laboratory (QLab) at Maryland 3 , College Park, Maryland 20742, USA
4. Department of Electrical Engineering, Stanford University 4 , Stanford, California 94305, USA