Abstract

Antihydrogen offers a unique way to test matter/antimatter symmetry. Antihydrogen can reproducibly be synthesized and trapped for extended periods. The ALPHA collaboration can interrogate the ground state energy with microwaves, determine the gravitational/inertial mass ratio and charge neutrality. The trapping apparatus has been upgraded, improving access for laser beams and microwaves. It includes a frequency stabilized laser system and a cryogenic enhancement cavity for two-photon excitation of the 1S-2S transition. Recent progress toward spectroscopy of trapped antihydrogen is presented with our latest results from Nature 529, 373 (2016).