[1] Univ Waterloo, Inst Quantum Comp, 200 Univ Ave West, Waterloo, ON N2L 3G1, Canada
[2] Univ Waterloo, Dept Phys & Astron, 200 Univ Ave West, Waterloo, ON N2L 3G1, Canada
[3] Austrian Acad Sci, Inst Quantum Opt & Quantum Informat IQOQI Vienna, Boltzmanngasse 3, A-1090 Vienna, Austria
[4] Tech Univ Wien, Atominst, Stadionallee 2, A-1020 Vienna, Austria