Quantum physics is one of the best-confirmed models of nature, and yet our common sense is challenged when we try to understand the quantum superposition of classically mutually exclusive states.  A series of recent experiments in Vienna has therefore been targeting the spatial superposition of isolated clusters and macromolecules. Our recent experiments have shown that large bound complexes, composed of up to almost thousand atoms, can be delocalized over hundred times their own size and still maintain quantum coherence in their center-of-mass motion over many milliseconds. This even holds when they are internally as hot as a 600 Kelvin, i.e. warmer than any living matter on Earth. Molecular interference is highly sensitive to many external perturbations but compatible with conservative force fields which do not measure the particle’s position. Quantum interferometry allows us to pattern genuine molecular nanostructures on millimeter-wide molecular beams. They are shown to be well-suited for precise measurements of magnetic, structural, electronic and optical properties of molecules even when these are in a widely delocalized quantum state.  We finally ask to what extent this principle holds when we head for particles of even higher mass and complexity and to what extent one may test theories which extend non-relativistic quantum mechanics to explain the effective transition between quantum and classical physics.

1        S. Nimmrichter, K. Hornberger, P. Haslinger, and M. Arndt, Phys. Rev. A 83, 043621 (2011).

2        K. Hornberger, S. Gerlich, P. Haslinger, S. Nimmrichter, and M. Arndt, Rev. Mod. Phys. 84, 157-173 (2012).

3        S. Gerlich, S. Eibenberger, M. Tomandl, S. Nimmrichter, K. Hornberger, P. J. Fagan, J. Tüxen, M. Mayor, and M. Arndt, Nature Communs. 2, 263 (2011).

4        S. Gerlich, et al., Nature Phys. 3, 711 (2007).