1. Center for Macroscopic Quantum States (bigQ), Department of Physics, Technical University of Denmark, Fysikvej 309, 2800 Kgs. Lyngby, Denmark
2. Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-363 Kraków, Poland
3. Department of Electrical Engineering, Technical University of Denmark, Ørsteds Plads, 2800 Kgs. Lyngby, Denmark
4. Institute for Quantum Optics and Center for Integrated Quantum Science and Technology (IQST), Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
5. Felix Bloch Institute for Solid State Physics, University of Leipzig, 04103 Leipzig, Germany