Stefan Ulmer is a chief scientist at RIKEN, Japan, founder and spokesperson of CERN’s BASE collaboration. He has received his PhD degree for the “first observation of spin flips with a single trapped proton”, which was a milestone experiment in proton/antiproton magnetic moment measurements. Following his work the BASE collaboration performed the most precise measurement of the magnetic moment of the proton with a fractional precision of 3 parts in a billion. In 2012 he joined the ASACUSA antihydrogen effort as a post-doc where he contributed to the production of the first beam of antihydrogen atoms, setting up the BASE experiment in parallel. In the first run of the BASE experiment (2014) he and his team performed the most precise test of CPT invariance with baryons by comparing the proton-to-antiproton charge-to-mass ratio with a fractional precision of 69 parts in a trillion. He invented a reservoir trap technique which enables BASE to operate antiproton experiments independent of accelerator cycles, and demonstrated in 2016 trapping of antiprotons for more than 405 days. In 2017 BASE reported on the most precise measurement of the magnetic moment of the antiproton with a fractional precision of 0.8 parts in a million. Very recently, BASE published a paper on the first observation of single antiproton spin transitions, which is a major step towards a measurement of the antiproton magnetic moment with a fractional precision on the parts-per-billion level. For his work on high-precision comparisons of the fundamental properties of protons and antiprotons he received the IUPAP young scientist award 2014.