Nobel Laureate Public Lecture Series:
Measuring Time - Atomic Clocks and Ultracold Atoms
5 Jul 2007, 2.30pm - 3.30pm
Lecture Theatre 2 (North Spine, NS4-2-36)
Professor Claude Cohen-Tannoudji
Nobel Laureate in Physics, 1997
Collège de France and Laboratoire Kastler Brossel;
École Normale Supérieure, Paris, France
Institut Francilien de Recherche sur les Atomes Froids
Abstract
Time measurement is based on the use of periodic phenomena like the rotation of the earth, the oscillation of a pendulum or the vibration of a quartz crystal. The oscillation frequency of the radiation emitted or absorbed by an atom undergoing a transition between 2 energy levels has the advantage of being universal since it is the same for all atoms of the same type. An atomic clock is an oscillator whose frequency is locked on the frequency of an atomic transition.
Ultracold atoms, which move with very low velocities, allow longer observation times which increase considerably the precision of the measurement of the atomic frequency. Recent spectacular progress in the realization of cesium atomic clocks using laser cooled atoms will be described, leading to relative frequency stability in the range of 10-16, which corresponds to an error less than one second in 3´108 years. The perspective of putting these clocks in a microgravity environment is very attractive. Several applications of these ultra precise atomic clocks are also being investigated and will be reviewed.
Brief Biography
Claude Cohen-Tannoudji (born April 1, 1933) is a French physicist working at the École Normale Supérieure in Paris, France.
Cohen-Tannoudji was educated at the École Normale Supérieure (ENS), Paris, receiving his doctorate in 1962. After graduating he continued to work as a research scientist in the department of physics at ENS, while also teaching quantum mechanics at the University of Paris VI from 1964 to 1973 and at the College of France from 1973 His lecture notes were the basis of the popular textbook Mécanique quantique he wrote with two of his colleagues. His research focus was on atom-photon interactions, and his group developed the dressed atom formalism.
In 1973, he became a professor at the Collège de France. In the early 1980s, he started to lecture on radiative forces on atoms in laser light fields. He also formed a laboratory there with Alain Aspect, Christophe Salomon and Jean Dalibard to study laser cooling and trapping.
Cohen-Tannoudji and his colleagues at ENS expanded on the work of Chu and Phillips, successfully explaining a seeming discrepancy in theory and devising new mechanisms for cooling and trapping atoms with laser light. In 1995 they cooled helium atoms to within eighteen-millionths of a degree above absolute zero (-273.15° C, or -459.67° F), with a corresponding speed of about two centimetres per second. Their work, and that of Chu and Phillips, furthered scientists' understanding of how light and matter interact. Among other practical applications, the techniques they developed can be used to construct atomic clocks and other instruments capable of an extremely high degree of precision.
His work there eventually led to the physics Nobel Prize of 1997 for the development of methods to cool and trap atoms with laser light, shared with Steven Chu and William Daniel Phillips. (Click here to read more.) At extremely low temperatures, the atoms move slowly enough to be examined in detail. He was also awarded the Young Medal and Prize in 1979, for distinguished research in the field of optics.
Please click here for the location map of Lecture Threatre 2 and poster.
This event is held in conjunction with First International Workshop on "Plasma Applications in Nanofabrication and Photovoltaic Solar Cells", 5 - 6 July 2007. Please click here for the program.
To register for this event, kindly email us at ias
ntu.edu.sg with the subject title: "Registration for talk by Prof Cohen Tannoudji".