1Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
3Institute for Quantum Science and Engineering (IQSE), and Texas A&M AgriLife Research and Hagler Institute for Advanced Study, Texas A&M University, College Station, Texas 77843-4242, USA