Prof. Gao's research focuses on understanding the structure of the nucleon in terms of quark and gluon degrees of freedom of Quantum Chromodynamics (QCD), search for QCD exotics, and fundamental symmetry studies at low energy to search for new physics beyond the Standard Model of electroweak interactions. Most of her work utilizes the novel experimental technique of scattering polarized electrons or photons from polarized gas targets. Her group has built a number of state-of-the-art polarized gas targets including H/D internal gas target and a high-pressure polarized 3He target for photon experiments using the High Intensity Gamma Source (HIGS) facility at the Duke Free Electron Laser Laboratory (DFELL). Currently, her group and collaborators from Indiana University are also employing such a high-pressure, thin-window polarized 3He target in a new search for spin-dependent short-range forces. She and her group are also collaborating on a challenging experiment aiming at a major improvement over the current limit on the neutron electric dipole moment. Such an experiment will make important contributions to the understanding of CP violation and to the search of New Physics beyond the Standard Model. Her research is being carried out at Duke University, the Thomas Jefferson National Accelerator Facility (JLab),the HIGS facility at DFELL, and the Fundamental Neutron Beam Line at the Spallation Neutron Source at the Oak Ridge National Laboratory.