[1] Ludwig Maximilians Univ Munchen, Fak Phys, Arnold Sommerfeld Ctr Theoret Phys ASC, Dept Phys, D-80333 Munich, Germany
[2] MCQST, Schellingstr 4, D-80799 Munich, Germany
[3] MTA Wigner Res Ctr Phys, Inst Solid State Phys & Opt, Strongly Correlated Syst Lendulet Res Grp, POB 49, H-1525 Budapest, Hungary
[4] Max Planck Inst Quantum Opt, Hans Kopfermann Str 1, D-85748 Garching, Germany