Roy Jay Glauber
1925–2018, New York City, United States, Newton, Massachusetts, United States
American theoretical physicist, 'father of quantum optics' — he built the theory of optical coherence and photon statistics.
Glauber entered Harvard in 1941 and, like many wartime colleagues, was recruited to the Manhattan Project at Los Alamos, where he computed fission chain reactions. He earned his PhD in 1949 under Julian Schwinger and returned to Harvard as professor in 1954.
In 1963 he built the quantum theory of optical coherence: introducing 'coherent states' and the correlation functions g⁽ⁿ⁾ that distinguish classical light, laser light, and nonclassical quantum states. This work defined the field of quantum optics and earned the 2005 Nobel Prize in Physics.
Nobel-winning work
The Hanbury Brown–Twiss interferometer (1956) measured photon 'bunching', showing starlight arrives in clumps — a phenomenon no classical optics theory could explain. In 1963, in three landmark Physical Review papers, Glauber gave the electromagnetic field a quantum mechanical treatment: every measurable intensity is a correlation of field operators E⁺, E⁻.
He showed coherent states — eigenstates of the annihilation operator — are the 'most classical' states possible, describing laser light exactly; while the correlation g⁽²⁾(0) = 1 separates classical light from squeezed, single-photon, and Fock states. This 'Glauber–Sudarshan P' framework is the standard language of quantum optics, foundation of today's optical quantum information. The 2005 Nobel recognized 'his contribution to the quantum theory of optical coherence'.
Workplaces: Harvard University
United States