After short-term positions at the University of California, Berkeley, the IBM Almaden Research Center in San Jose, California, and the Mathematical Sciences Research Institute in Berkeley, he joined the faculty of Hebrew University in 1986. In 1999 he also took a position at the Institute for Advanced Study, and in 2003 he gave up his Hebrew University position to take up full-time residence at the IAS.
After temporary positions at the University of California, Berkeley, IBM Almaden Research Center in San Jose, California, and the Mathematical Sciences Research Institute in Berkeley, he became a faculty member at Hebrew University in 1986. He also took on a position at the Institute for Advanced Study in 1999 and left his position at Hebrew University to become fully employed by the IAS in 2003.