[1] Leiden Univ, Inst Lorentz, POB 9506, NL-2300 RA Leiden, Netherlands
[2] Austrian Acad Sci, Inst Quantum Opt & Quantum Informat, Boltzmanngasse 3, A-1090 Vienna, Austria
[3] Univ Vienna, Fac Phys, Vienna Ctr Quantum Sci & Technol, Boltzmanngasse 5, A-1090 Vienna, Austria