Antimatter gravity studies with interferometry

There has never been a direct measurement of the gravitational force on antimatter. This paper describes a possible measurement of this force by measuring the phase shift of neutral antimatter in a transmission-grating interferometer caused by the Earth’s gravitational field. This experiment avoids the severe problem of shielding stray electromagnetic fields necessary for making a gravity measurement with charged particles, and also avoids the need to trap neutral particles. The neutral antimatter for this experiment could be either antihydrogen, positronium, or antineutrons.