 When his original doctoral thesis adviser at Aarhus retired, Phillips took over as his thesis adviser.In 1990 and 1992, he was a guest researcher at NIST; in 1993, he was a postdoctoral fellow at University of Maryland; from 1993 to 1998, he was an assistant professor at the University of Arizona; from 1998 to 2002, he was associate professor at the University of Arizona; and from 2002 he has been a full professor at the University of Arizona.He has co-authored more than twenty papers.