1. Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
2. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
3. Wigner Research Centre for Physics, H-1525 Budapest, P.O.Box 49, Hungary
4. BME-MTA Lendület Quantum Information Theory Research Group, Budapest, Hungary
5. Mathematical Institute, Budapest University of Technology and Economics, P.O.Box 91, H-1111, Budapest, Hungary