- Person
- Roy Glauber
- Lived
- 1925–2018
- Field
- Theoretical physics
- From
- American
The story
Roy Glauber was born in New York City in 1925 and grew up in a family of modest means during the Depression. He built his own telescope as a boy, went to the new Bronx High School of Science and won a scholarship to Harvard. At eighteen he worked as a theorist on the Manhattan Project at Los Alamos, and after earning his PhD at Harvard in 1949 he spent his career there as a professor of physics.
Since Einstein’s work of 1905, physicists had known that light comes in packets of energy called photons. In practice, though, almost all optics was done by treating light as a classical wave, and quantum theory was thought unnecessary for visible light. Two developments in the late 1950s changed that. The laser was invented, producing a new and remarkably pure kind of light, and the astronomers Robert Hanbury Brown and Richard Twiss found that photons from an ordinary source tend to arrive at detectors in clumps. Nobody had a consistent theory of what a light detector actually records.
In 1963 Glauber supplied one. He used quantum field theory to describe how a photodetector absorbs photons and how the counts of one or several detectors are correlated. He introduced the coherent state, the quantum description of ideal laser light, and showed that the bunching seen by Hanbury Brown and Twiss is a natural result of the random nature of thermal light, while a perfect laser beam shows no bunching at all. His theory also predicted kinds of light that no classical wave can produce, such as streams in which photons arrive more evenly spaced than chance would allow; such light was later observed. The Indian-American physicist E. C. George Sudarshan published a closely related description the same year.
These papers founded quantum optics, now one of the most active areas of physics. The quantum noise of light that Glauber described sets the final limit on the precision of optical measurements. His framework underlies single-photon sources and detectors, quantum key distribution, which uses individual photons to share encryption keys that cannot be intercepted unnoticed, experiments on entanglement and teleportation, and photonic quantum computers. Gravitational-wave observatories now use squeezed quantum light, described in the same language, to improve their sensitivity. Glauber shared the 2005 Nobel Prize in Physics for this work and kept teaching at Harvard into his eighties.
Why it matters
Glauber’s quantum theory of light is the foundation of quantum optics, used today in precision laser measurement, quantum-secure communication and the race to build quantum computers.
About Roy Glauber
New York-born Harvard physicist who wrote the quantum theory of light in 1963, founding quantum optics: the science behind laser physics, quantum encryption and quantum computing. Nobel Prize 2005.
Sources
- The Nobel Prize in Physics 2005, Popular information NobelPrize.org
- Roy J. Glauber, Facts NobelPrize.org
- Roy Jay Glauber, 93 (memorial minute) Harvard Gazette
- Roy J. Glauber Wikipedia
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