1. E.
L. Ginzton Laboratory, Stanford University, Stanford, California 94305, United States
2. 3rd
Institute of Physics, IQST, and Research Center SCOPE, University of Stuttgart, 70569 Stuttgart, Germany
3. Center
for Quantum Information, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea
4. Department
of Physics, Chemistry, and Biology, Linköping University, SE-58183 Linköping, Sweden
5. National Institutes for Quantum and Radiological Science and Technology (QST), Takasaki, Gunma 370-1292, Japan