1. Centre de Nanosciences et de Nanotechnologies (C2N), CNRS UMR 9001, Université Paris-Sud, Université Paris-Saclay, 91120 Palaiseau, France
2. Istituto Nazionale di Ottica, Bose-Einstein Condensation Center, University Trento, 38123 Trento, Italy
3. Laboratorio TASC, CNR-IOM, Area Science Park, S.S. 14 km 163.5, Basovizza, I-34149 Trieste, Italy