1. Department of Physics and Illinois Quantum Information Science and Technology Center (IQUIST), University of Illinois Urbana-Champaign, Urbana, IL, USA
2. James C. Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, USA
3. SRI International, Arlington, VA, USA
4. Quantum Information Science Section, Oak Ridge National Laboratory, Oak Ridge, TN, USA