Wolfgang P. Schleich, born in 1957, is head of the Institute of Quantum Physics at the University of Ulm, Germany, and Adjunct Professor at the University of North Texas in Denton, USA. While working at the Universities of New Mexico, Albuquerque, of Texas at Austin and the Max Planck Institute for Quantum Physics, Garching, Germany, he has collaborated with world leaders in physics such as M.O. Scully, J.A. Wheeler and H. Walther. Professor Schleich has published more than 230 papers on problems of quantum optics, foundations of quantum mechanics and general relativity and is the author of the highly acclaimed textbook Quantum Optics in Phase Space. For his work he has received numerous awards and honors, including the Ernst Abbe Medal of the International Commission for Optics, the Gottfried Wilhelm Leibniz Prize of the German Science Foundation and the Max Planck Award. He is a Fellow of the Institute of Physics, the American Physical Society and the Optical Society of America and has been elected a member of several academies, such as the Leopoldina, the Heidelberg Academy of Science, and the Royal Danish Academy of Sciences and Letters. Herbert Walther (1935-2006) received his Ph.D. from the University of Heidelberg in 1962. After working at various universities in Germany, France and the United States, Professor Walther accepted a post as Professor of Physics at the University of Munich in 1975, from which he took retirement in 2003. From 1981, Professor Walther also worked for the Max Planck Society. He founded the Max Planck Institute of Quantum Optics in Garching, and headed the Institute as its Director until his retirement. From 1990 to 1996, he acted as the Max Planck Society's Vice President. Professor Walther was a Fellow and member of many professional physics organizations and scientific boards. He was awarded numerous honours and awards, among them the Max Born Prize (1978) and the Humboldt Medal (1998).