Levitated solids in the quantum regime as quantum sources of gravity: The decoherence challenge

The quantum optical control of solid-state mechanical devices, quantum optomechanics, has emerged as a new frontier of light-matter interactions. Objects currently under investigation cover a mass range of more than 17 orders of magnitude - from nanomechanical waveguides to macroscopic, kilogram-weight mirrors of gravitational wave detectors. Applying this approach to levitated solids opens up new ways of coherently controlling the motion of massive quantum objects in engineerable potential landscapes. Our team in Vienna is exploring and further developing this toolbox with the goal to realize quantum sources of gravity in the lab: superpositions of gravitationally distinct states of a massive object. One main challenge is to achieve sufficiently long coherence times in the presence of residual background gas, blackbody radiation, vibrations, imperfect control operations, etc., while making the object more massive and more delocalized. I will review basic considerations, experimental techniques and open questions in our efforts to minimize effects of decoherence in these experiments.