1. Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria.
2. Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, A-1090 Vienna, Austria.
3. Department of Physics and Astronomy, Centre for Engineered Quantum Systems, Macquarie University, Sydney, New South Wales 2109, Australia.