Claude Cohen-Tannoudji

Claude Cohen-Tannoudji is a French physicist whose work on laser cooling and trapping atoms helped earn him the 1997 Nobel Prize in Physics.

Steven Chu: An American physicist who shared the 1997 Nobel Prize in Physics for developing methods to cool and trap atoms with laser light. Cohen-Tannoudji shared the prize with Chu, whose independent experiments demonstrated laser cooling.
Laser cooling: A family of techniques that use light to reduce the motion and temperature of atoms or other particles. Cohen-Tannoudji developed central methods within this broader approach.
Bose–Einstein condensate: A state of matter in which many bosonic particles occupy the same lowest-energy quantum state. Laser cooling helps prepare atomic samples cold enough to reach this quantum phase.
Photon momentum: The momentum carried by a photon, proportional to its energy and inversely proportional to the speed of light. Absorption and emission of photons transfer momentum and change atomic motion.
Doppler limit: The minimum temperature predicted for ideal Doppler cooling of a two-level atom. Experiments below this limit exposed the need for the sub-Doppler mechanisms Cohen-Tannoudji helped explain.
William D. Phillips: An American physicist who shared the 1997 Nobel Prize in Physics for laser cooling and trapping atoms. Phillips was the third laureate recognized alongside Cohen-Tannoudji and Chu.
Doppler cooling: A laser-cooling method that slows atoms through frequency-selective absorption and photon momentum transfer. It provides the basic cooling mechanism that Cohen-Tannoudji's sub-Doppler methods surpassed.
Atomic clock: A clock that measures time using the resonant frequencies of atoms. Cold trapped atoms can reduce motion-related errors in precision timekeeping.
Radiation pressure: Force exerted on matter when electromagnetic radiation transfers momentum to it. Repeated photon absorption produces the forces used to slow and confine atoms.
Laser cooling below the Doppler limit: Laser cooling that reaches atomic temperatures lower than the standard Doppler-cooling limit. This experimental advance motivated the theoretical account of polarization-gradient cooling.

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