Searching for non-Newtonian gravity with optically levitated microsphere in vacuum*

In this talk, I will present our experimental approach [1] towards the search of deviations from Newtonian gravity at short range predicted by several theories beyond the Standard model- including supersymmetry and string theory. In our experiment, we use an optically levitated and cooled dielectric nanosphere in vacuum as a micromechanical sensor which can have extremely high sensitivity of $\sim 10^{-21}N/\sqrt{Hz}$. I will discuss our progress towards cooling of the center-of-mass motion of the trapped bead and the calibration of the sensor using known modulated electric fields.\\[4pt] [1] Andrew A. Geraci, Scott B. Papp, and John Kitching, Phys. Rev. Lett. 102, 101101 (2010)