He started his career at Stockholm University, where he got hooked on particle physics after spending the summer of 1998 at CERN as a summer student. He graduated in 2001 and continued at Stockholm University for his doctoral studies, where his research concerned top quark physics at the Tevatron collider outside Chicago. He defended his Ph. D. thesis in 2006 and spent the following four years as a postdoc at the University of Michigan, before joining KTH as an assistant professor in 2011. He is a member of the ATLAS collaboration at CERN, and for many years now Jonas has been involved the search for, and the subsequent discovery of, the Higgs particle in ATLAS.