Graviton-Photon Conversion in Atoms and the Detection of Gravitons

We study graviton-photon conversion in ground-based experiments. From graviton to photon tran- sition, we calculate the cross section of graviton-atom interaction in the presence of spherical atomic electric fields; the obtained results hold for graviton energy around 100 keV - 1 GeV and would be enhanced by crystal structures, thus it gives a chance to catch MeV level gravitons from the universe with current neutrino facilities. From photon to graviton transition, we propose an experiment using entangled pho- ton pairs to count missing photons passing through transverse magnetic tunnel, which could be used to verify the energy quantization of gravitational field.