Illustration of the US physicist Roy Glauber (1925-2018). Glauber obtained a PhD in physics in 1949 from Harvard University, Cambridge, Massachusetts, USA. Glaubers paper The Quantum Theory of Optical Coherence was published in Physical Review in 1963. It established the basis for applying quantum physics to optical phenomena, forming a new field of research known as quantum optics. Glaubers theories were able to describe the differences between hot sources of light, such as light bulbs, and lasers, which have a specific frequency and phase. Glauber received the 1995 Nobel Prize in Physics along with John Hall and Theodor Hansch for their contribution to the understanding of light.