1. Evatec AG, Hauptstrasse 1a, CH-9477 Trübbach, Switzerland
2. CEA-LETI/Minatec, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
3. Department of Condensed Matter Physics, Masaryk University, Kotlářska 2, CZ-61137 Brno, Czech Republic
4. CEITEC, Masaryk University, Kamenice 5, CZ-60177 Brno, Czech Republic