1. Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria
2. Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, 6020 Innsbruck, Austria
3. Department of Physics, Harvard University, Cambridge, MA 02138
4. Department of Physics, University of Colorado, Boulder, CO 80309
5. Joint Institute for Laboratory Astrophysics, University of Colorado and National Institute of Standards and Technology, Boulder, CO 80309
6. Université Grenoble Alpes, CNRS, Laboratoire de Physique et Modélisation des Milieux Condensés, Grenoble 38000, France