Cohen-Tannoudji, Claude (1933-…), a French physicist, contributed to the technique of trapping atoms—slowing them down until they are almost stationary, so that they can be studied without being disturbed by the constant battering of other atoms. This technique enables scientists to obtain precise measurements of the properties of the atoms, and promises to make new devices possible, including clocks of unprecedented accuracy. Cohen-Tannoudji shared the 1997 Nobel Prize in physics with two Americans, Steven Chu and William D. Phillips, for their independent work in the same field (see Chu, Steven ; Phillips, William Daniel ).
Claude Nessim Cohen-Tannoudji was born on April 1, 1933, in Constantine, Algeria. Algeria was then a French colony. He carried out research in physics at the National Center for Scientific Research (CNRS) in Paris from 1960 to 1964, gaining a Ph.D. from the University of Paris in 1962. He was a professor at the University of Paris from 1964 until 1973, when he became a professor at the College de France, Paris. He did research at the Ecole Normale Superieure from 1984.
Cohen-Tannoudji was on the faculty of the College de France and the Ecole Normale Superieure at the time that he did his Nobel Prize-winning work. Atom-trapping was a rapidly developing field. Steven Chu’s group in the United States had developed a technique for slowing atoms and catching them in a “trap” for study. At the U.S. National Institute of Standards and Technology (NIST), Phillips applied Chu’s technique to cool atoms to extremely low temperatures, about 40 millionths of a Celsius degree above absolute zero. Absolute zero is the lowest possible temperature, –273.15 °C.
The temperature that Phillips achieved was below what scientists had thought possible. Cohen-Tannoudji was one of the theorists who rose to the challenge of explaining how such a low temperature was possible. He used quantum theory, which explains the behavior of matter and energy at the subatomic scale, to explain the low temperatures observed. Then, with other workers at the Ecole Normale Superieure, he was able to cool atoms even further, to within two millionths of a degree Celsius above absolute zero. Since then, researchers have produced temperatures of a few billionths of a degree.
