Measuring Small-Scale Gravitational Forces

We are motivated by the question how well one can isolate gravity as a dominant coupling force between small-scale physical systems in table-top experiments. In other words: how small can one make a gravitational source mass and still detect its gravitational coupling to a nearby test mass? We have recently introduced a micromechanical method that should allow for a proof-of-concept demonstration for objects on the scale of millimeters and tens of milligrams, which already improves the current limit for sensing the gravitational field of a small source mass by three orders of magnitude. With further improvements this method provides an alternative high-precision measurement of the gravitational constant, which may be less subject to conventional source-mass related disturbances of other approaches. In the long run, the ability to extend the control over gravitational coupling into the microscopic domain may enable a new generation of quantum experiments, in which the source mass character of the quantum systems start to play a role.