Generation of Einstein-Podolsky-Rosen State via Earth's Gravitational   Field
  Although various physical systems have been explored to produce entangled states involving electromagnetic, strong, and weak interactions, the gravity has not yet been touched in practical entanglement generation. Here, we propose an experimentally feasible scheme for generating spin entangled neutron pairs via the Earth's gravitational field, whose productivity can be one pair in every few seconds with the current technology. The scheme is realized by passing two neutrons through a specific rectangular cavity, where the gravity adjusts the neutrons into entangled state. This provides a simple and practical way for the implementation of the test of quantum nonlocality and statistics in gravitational field. 
Jun-Li Li and Cong-Feng Qiao
quant-ph hep-ph