Laureate Biography
Claude Cohen-Tannoudji shared the 1997 Nobel Prize in Physics with Steven Chu and William D Phillips for developing methods to cool and trap atoms using streams of laser light. Under normal conditions, atoms in a gas move around randomly at hundreds of metres per second, far too fast to examine in any detail, but Cohen-Tannoudji helped to create ways of slowing atoms in their tracks long enough so that their behaviour can be studied.
Cohen-Tannoudji was born on 1 April 1933 in Constantine, Algeria. His family had moved from Tangier to Algeria in the sixteenth century; the name Cohen-Tannoudji meaning ‘the Cohen family from Tangier’.
His father was self-taught, but as Cohen-Tannoudji recalls, he had “a great intellectual curiosity”, and it was from his father that Cohen-Tannoudji got his passion for studying, learning and sharing knowledge.
He went to school in Algiers before leaving the country in 1953 to study at the École Normale Supérieure (ENS) in Paris, one of the grandes écoles. While there, he attended lectures by the Nobel Laureate Alfred Kastler, and was inspired to switch from mathematics to physics. In 1955, Cohen-Tannoudji attended the Les Houches summer school run by the University of Grenoble in the Alps. It was an intensive and stimulating two months, with six lectures each day from renowned scientists discussing problems in theoretical physics, and this provided him with a profound insight into the area.
As he was finishing his diploma at the ENS in 1957, Cohen-Tannoudji met Jacqueline, and they married the following year. After he left the ENS, Cohen-Tannoudji was conscripted into military service, which lasted for 28 months — a longer period than normal because of the Algerian War, although he spent part of this assigned to the scientific department.
In 1960, he began a PhD at the CNRS (Centre national de la recherche scientifique), supervised by Kastler. Following his graduation with a doctorate in 1962, Cohen-Tannoudji took a teaching position at the University of Paris, and was appointed Professor at the Collège de France in 1973. At the Collège, lectures are open to all, and professors have free choice over their topic (but may not repeat that of a previous year), an environment that Cohen-Tannoudji says allowed him to explore lines of research that he might otherwise have ignored.
In 1984, he formed a new research group at the Collège to look into cooling atoms with laser light and trapping them, a concept originally proposed in 1975 by Nobel Laureates Theodor Hänsch and Arthur Schawlow. There, Cohen-Tannoudji built upon the breakthroughs that Chu and Phillips had made in cooling gaseous atoms, using a web of laser light to remove their kinetic energy, and slowing them down as if they were trapped in a thick liquid, or ‘optical molasses’ as Chu called it.
Cohen-Tannoudji devised ways of overcoming the limits to which atoms can be cooled, by preventing very cold atoms from absorbing light, and this allowed atoms to be chilled to 0.2 millionths of a (Celsius) degree above absolute zero and keep them floating. These breakthroughs led to many applications; laser cooling and trapping methods are used to create extremely accurate atomic clocks, and high-precision devices for measuring gravity, where the more the atoms are under control within the mechanism, the more accurate it can be.
Among other distinctions, Cohen-Tannoudji has received the Gold Medal of the Centre National de la Recherche Scientifique, and he has been a member of the French Académie des Sciences since 1981.
Nobel Prize in Physics 1997
Claude Cohen-Tannoudji’s Nobel Lecture
Claude Cohen-Tannoudji’s lab page
Wikipedia: Claude Cohen-Tannoudji
