Tests of Gravity with Antimatter

Einstein's Weak Equivalence Principle (WEP) demands that all objects fall with the same acceleration regardless of their composition, and experiments with ordinary matter have verified this with extraordinary sensitivity. When it comes to antimatter objects though, a direct measurement of gravitational acceleration was achieved only recently in the ALPHA-g experiment by carefully releasing trapped antihydrogen atoms from a magnetic bottle. The best fit value from this dataset was 0.75 ± 0.13 (stat. + syst.) ± 0.16 (simulation) in units of the gravitational acceleration of ordinary matter, and is thus in agreement with the WEP prediction.

In this talk I will describe some of the challenges of measuring the very weak effects of gravity on single antihydrogen atoms, and explain the magnetic bias technique which forms the basis of gravitational measurements in ALPHA-g. Finally I will outline developments towards higher precision measurements of antimatter gravity in ALPHA-g