1. Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
2. Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, 2800 Kgs. Lyngby, Denmark
3. CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples, Italy
4. Dipartimento di Fisica “E. Pancini”, Compl. Univ. di Monte S. Angelo, Università di Napoli “Federico II”, Via Cintia, 80126 Napoli, Italy
5. Department of Physical Sciences and Technologies of Matter, CNR-DSFTM NFFA Trieste Area Science Park, Basovizza Strada Statale 14, 34149 Trieste, Italy