After the war, he went to Princeton to attend the seminar of Niels Bohr on quantum mechanics. He returned to France and introduced the first general courses of quantum mechanics in France, at the University of Orsay and joined the newly created atomic energy agency, the Commissariat à l'énergie atomique (CEA) where he stayed until the end of his career. His textbook on quantum mechanics (Dunod 1959) has trained generations of French physicists.