May 9, 1927–February 9, 2001

BY ROBERT J. SCULLY, MARLAN O. SCULLY, AND H. JEFF KIMBLE

LEONARD MANDEL WAS the Lee DuBridge Professor of Physics and Optics at the University of Rochester: masterful scientist, exemplary teacher, generous colleague, and beloved family man. He is widely credited with being one of the founding fathers of the field of quantum optics, which sprung from the marriage of quantum mechanics and optics in the 1960s into one of the most exciting areas in modern science. He made seminal contributions to experimental and theoretical problems of optical coherence, laser physics, and quantum optics, including laser phase transitions, locality violations in optics, tests of quantum mechanics, and nonclassical states of light. A central theme of his research was a continuing quest to explore and elucidate the quantum character of light by way of insightful theoretical analyses and a set of pioneering experiments that have become landmarks in the field. He deepened our understanding of quantum mechanics in important and lasting ways through ingenious experiments that provided convincing demonstrations and precise tests of many of the most counterintuitive aspects of the quantum nature of light. Rarely has any one individual so intimately investigated and so dramatically advanced our understanding of the quantum mechanical nature of light.