Abstract: There is no experiment today that tells us if the laws of quantum physics also apply to gravity. One possible approach is to make a quantum object so massive that we can directly measure its gravitational field. This would allow to probe gravitational phenomena that originate in the quantum superposition of a source mass – and hence to experimentally distinguish between classical and quantum field theoretic predictions of gravity. Realizing such quantum sources of gravity in the lab requires to explore extreme regimes of both quantum and gravity experiments, specifically: delocalized motional quantum states of sufficiently massive solid-state objects, as well as gravity experiments on the microscopic scale. I review the current status in the lab and the challenges to be overcome for future experiments.

Markus Aspelmeyer is Professor of Physics at the University of Vienna and Director at the Institute for Quantum Optics and Quantum Information - Vienna (IQOQI-Vienna) of the Austrian Academy of Sciences. Aspelmeyer studied Physics and Philosophy in Munich. After completing his doctorate in solid-state physics at Ludwig Maximilian University in Munich in 2002, he moved into the field of quantum optics, where he worked as a Feodor Lynen Fellow of the Alexander von Humboldt Foundation with Anton Zeilinger, later winner of the Nobel Prize in Physics, at the University of Vienna. After establishing a research group as a senior scientist at IQOQI Vienna of the Austrian Academy of Sciences, he was appointed to the University of Vienna in 2009. Since 2019, he has also been the scientific director of IQOQI Vienna. In 2010 and 2011, Aspelmeyer was a guest at the University of Potsdam and Humboldt University Berlin as a Friedrich Wilhelm Bessel Research Award winner. His current research focuses on the fascinating mysteries surrounding quantum physics and gravity. He has received numerous international awards for his work on quantum control of macroscopic solid-state systems (quantum optomechanics).