Graham attended the Karls-Gymnasium in
Stuttgart and studied at the
University of Stuttgart, where in 1967 he earned under
Hermann Haken his physics
Diplom (quantum fluctuations of the
optical parametric oscillator) and in 1969 his PhD (
Lichtausbreitung in laseraktiven fluktuierenden Medien, "Light Propagation in Laser-active Fluctuating Media"). Continuing this work, he applied the theory of cooperative systems publicized by Haken as "Synergetik" (
Synergetics) in quantum optics. As a post-doc, he was a guest scientist at
New York University and, after his
Habilitation in 1971, scientific advisor and professor at the University of Stuttgart. From 1975 he was a professor at the
Universität Duisburg-Essen, where he is now retired as professor emeritus. He was there also dean and prorector for research. He worked on extremely diverse areas of quantum theoretical statistical mechanics, apart from laser theory also in the 1990s with the theory of
Bose–Einstein condensate. In 2009 he received the
Max Planck medal, the highest honor of the
DPG in theoretical physics for his contributions in the areas of quantum optics, the statistical mechanics of open stationary systems outside thermodynamic equilibrium, quantum fluids and quantum gases as well as quantum chaos (according to the Laudatio of the Max Planck medal 2009) and his contributions to quantum aspects of cosmology and gravitation. == Selected works ==