Search for non-Newtonian interactions at micrometer scale with a levitated test mass

The universal law of gravitation has undergone stringent tests for many decades over a significant range of length scales, from atomic to planetary. Of particular interest is the short distance regime, where modifications to Newtonian gravity may arise from axion-like particles or extra dimensions. We have constructed an ultra-sensitive force sensor based on optically-levitated microspheres with a force sensitivity of $10^{-16}N/ \sqrt{Hz}$ for the purpose of investigating non-Newtonian forces that couple to mass with a characteristic scale of $\sim 10 \mu$m. 

In this talk I will present the first investigation of the inverse-square law using an optically levitated test mass. This technique is complementary to other methods used to search for new forces in the short range regime as all the scales involved in the experiment are the same order of magnitude as the characteristic length scale being probed. In addition, the measurement is currently not limited by fundamental physical limitations and ongoing improvements of the system targeting better background mitigation and modeling, together with improved force sensitivity, are expected to allow a search in a new region of the parameter space.