1. JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University 1 , 52074 Aachen, Germany
2. Peter Grünberg Institute, Forschungszentrum Jülich GmbH 2 , 52425 Jülich, Germany
3. Department of Physics, RWTH Aachen University 3 , 52074 Aachen, Germany