Claude Cohen-Tannoudji @UFRJ

Claude Cohen-Tannoudji, Nobel prize winner, co-author of one of the best quantum mechanics book ever written, the man, the legend… will be visiting the physics department of the Federal University of Rio de Janeiro next week. That is an unmissable event!

Cohen was really kind to offer delivering two talks at UFRJ. The first seminar, on Monday, will be more direct towards quantum optics/information researches. The title is: “Light shifts. From optical pumping to cavity quantum electrodynamics.” Of course, even if you don’t work with these subjects you should check out the seminar! The second seminar, on Thursday, is actually a colloquium, entitled “Laser Cooling and Trapping of Atoms”. Okay, you probably know that, but in any case, that’s the subject Cohen (together with Steven Chu and William Daniel Phillips) got the Nobel for!! But don’t even think that he’ll be talking about physics of the 90’s (he got the Nobel in 1997). The number of applications of optical cooling and the physics behind it just don’t stop growing. Cohen will survey those and show how they changed the way we understand the light-matter interaction… or literally how we see the world!

The details of both talks are below.  Those, like myself, that spent/spend days and days learning from the pages of Cohen’s quantum mechanics books, know how crystal-clear and deep his explanations are. Don’t miss this chance!! See you there.



Speaker: Claude Cohen-Tannoudji (Ecole normale supérieure)

Title:  Light Shifts — From Optical Pumping to Cavity QED

Time/Place: Monday 01.12,  15:30hs / Centro de Tecnologia do Fundão, Bloco A, sala 343.

Summary: Light shifts, which have been discovered during the early days of optical pumping, can be simply interpreted in a dressed atom approach. They were first considered as a source of perturbation in high-resolution spectroscopic measurements since they modify the frequency of the atomic transitions. It appeared later on that they could also have interesting applications as a tool for manipulating atoms. For example, spatially dependent light shifts associated with light intensity gradients give rise to potential wells, which can trap neutral atoms if they are sufficiently cold. The light shifts associated with a laser standing wave produce a system of spatially periodic potential wells, called optical lattice. The interest of this periodic structure is that the motion of an atom in an optical lattice mimics the motion of an electron in a crystal, allowing a better understanding of phase transitions in condensed matter such as the superfluid-Mott insulator transition. Combination of spatially periodic light shifts with spatially modulated optical pumping rates is also at the origin of efficient laser cooling mechanisms, like the Sisyphus cooling mechanism. Finally, the light shift produced by a single photon trapped in high-Q cavity on an atom crossing the cavity can be used for detecting the presence of this photon in the cavity without destroying it, as demonstrated by Serge Haroche and his group.



Speaker: Claude Cohen-Tannoudji (Ecole normale supérieure)

Title: Laser Cooling and Trapping of Atoms

Time/Place: Thursday 04.12,  11:00hs / Centro de Tecnologia do Fundão, Bloco A, sala 343.

Summary: Conservation laws are very important in quantum physics. Two examples of applications will be given in this lecture. The first one is optical pumping which uses transfer of angular momentum from polarized photons to atoms to produce highly polarized atomic gases allowing a very sensitive detection of magnetic resonance. The second example is laser cooling which uses transfer of linear momentum from photons to atoms to produce large radiative forces acting on these atoms and allowing one to cool them at extremely low temperatures. Various applications of optical pumping and laser cooling will be briefly reviewed showing how long term basic research is essential for improving our understanding of the world and for giving rise to a wealth of important applications.


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