1. Institute of Physics, Albert-Ludwig University Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany
2. DISAFA, Università di Torino, I-10095 Grugliasco, Italy
3. EUCOR Centre for Quantum Science and Quantum Computing, Albert-Ludwig University Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany