1. Fraunhofer Institute for Applied Optics and Precision Engineering IOF Albert‐Einstein‐Str. 7 Jena 07745 Germany
2. Institute for Quantum Optics and Quantum Information Austrian Academy of Sciences Boltzmanngasse 3 Vienna A‐1090 Austria
3. Fraunhofer Institute for Industrial Mathematics Fraunhofer‐Platz 1 Kaiserslautern 67663 Germany
4. Friedrich‐Schiller‐University Jena Abbe Center of Photonics Albert‐Einstein‐Str. 6 Jena 07745 Germany