Projet ANR-07-BLAN-0137 – MICPAF : Microscopie en champ proche d'un atome froid
Programme : Blanc (BLANC) 2007
Année de financement : 2007
Coordinateur du projet : UNIVERSITE DE LILLE I [SCIENCES ET TECHNOLOGIES] (UNIVERSITE DE LILLE I [SCIENCES ET TECHNOLOGIES])
Partenaires : Centre national de la recherche scientifique; Université Lille 1 - Sciences technologies
Montant : 260000.0 euros
Date de début : 2007
Durée : 48 mois
Résumé : "The present project is proposed by two teams. The ""Quantum chaos"" group of the Laboratoire de Physique des Lasers, Atomes et Molécules (PhLAM), at the Université des Sciences et Technlogies de Lille, has been working on experimental and theoretical studies of quantum dynamics of laser-cooled atoms for many years, especially in the helm of quantum chaos, in which it acquired an international visibility. The ""Dynamics of coulombian systems"" group of the Laboratoire Kastler-Brossel (LKB) at Ecole Normale Supérieure, has been a world leader in the theory of quantum chaos for two decades. The two teams have been fruitfully collaborating since 1999. In the present project, the PhLAM team will be mostly in charge of the experimental activities, and the LKB will be mostly responsible for modelizing and numerical simulations. -  Laser-cooled atom physics has been playing a major role in atomic physics and quantum optics for twenty years of so. The importance of the subject was even increased by many important breakthroughs: the experimental observation of Bose-Einstein condensates (1995), the production of quantum-degenerate Fermi gases (1999) and the possibility of using one-atom traps for quantum information processing (2001). A relevant part of this effort concentrates in the dynamics of cold atoms (in the quantum-degenerate regime or not) trapped in optical potentials. This allowed in particular the observation of Bloch oscillations (1996), of the Wannier-Stark ladder (1996), and of the Mott transition (2002), establishing a bridge with solid-state physics. Atoms trapped in optical potentials have also been used in studies of quantum chaos and for the manipulation of ""q-bits"". Despite these remarkable advances, most experimental observations of quantum dynamics in optical potentials are still confined to the momentum space, using either time-of-flight techniques or stimulated Raman spectroscopy. Two factors make it very difficult to observe this dynamics directly in position space. Firstly, the width of the wells in an optical potential is typically half the wave-length, forbidding a direct measurement of the position by observing the fluorescence of the atom. Secondly, one generally works with clouds or condensates made of thousands to millions of atoms whose spatial extension is of the order of a hundred microns, much larger than the typical sizes involved in quantum dynamics (which usually involves only a few neighbor wells); these effects are thus difficult to detect in the much larger atom cloud or condensate. -  The present project proposes a solution to these difficulties, allowing the detection of atomic dynamics in the position space with a resolution comparable (or even better) than the width of a potential well. This shall be achieved by trapping a single atom in an optical potential and bringing it within a sub-lambda distance of a microstructured optical fiber, presenting sub-lambda structures. Such conditions shall allow us to make a near-field image of the atom, inspired from a technique that has been used for many years for sub-lambda microscopy of solids. Our initial aim is to obtain a resolution of the order of half the wavelength, or 400 nm, which shall allow us to determine non-ambiguously the individual potential well in which the atom is trapped without the need of performing long-time averaging. -  In developing this project, we must surmount challenging difficulties. However, these difficulties often imply an interesting underlying physics that deserves by itself to be studied. For example, placing an atom at a sub-micron distance of a microstructured material will modify the atom's properties, as its spontaneous emission rate. This is a very interesting experiment that is just starting to attract the attention of the community. In the same vein, the light issued from a microstructured fiber at sub-lambda distances of an atom can be used to manipulate the atom with unprecedented precision and finesse.