John completed his PhD in physics at the University of California at Berkeley in 1991. He was a postdoctoral fellow at the University of Washington in Seattle from 1991 to 1994 and an Alexander von Humboldt Fellow and Max Planck Research Fellow at the Max Planck Institut für Strömungsforschung in Göttingen from 1994 to 1998. John returned to Australia taking up a Queen Elizabeth II Fellowship in 2000.
He has been a Professor in the Research School of Physics and Engineering since 2008 and was Deputy Director of the School from 2012 to 2016. He was a member of the Australian Research Council College of Experts from 2015 to 2018. He served as an elected staff representative on ANU Council from 2012 to 2014 and served on the University Education Committee from 2014 to 2016. John was Deputy Chair of ANU Academic Board from 2015 to 2017.
He is a Senior Fellow of the Higher Education Academy, Head of the Department of Quantum Science and Chair of the ANU Defence Working Group.