In 1958, P.W. Anderson predicted the localization [1] of electronic wave functions in disordered crystals, and the resulting absence of diffusion. It has been realized later that Anderson Localization is ubiquitous in wave physics [2] as it originates from the interference between multiple scattering paths, and this has prompted an intense activity to observe it with light waves, microwaves, sound waves, and electron gases, but to our knowledge there was no direct observation of exponential spatial localization of matter-waves (electrons or others). We have observed directly [3] exponential localization of the wave function of ultracold atoms released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle. We will present this work, and the prospects of extending that type of study to quantum gases in higher dimensions (2D and 3D) and with controlled interactions. We will also discuss its significance in the rapidly growing domain of quantum simulators aiming at studying difficult problems of Condensed Matter.[1] Anderson, P.W. Absence of diffusion in certain random lattices. Phys. Rev. 109, 1492-1505 (1958).[2] Van Tiggelen, B. Anderson localization of waves. In Wave diffusion in complex media 1998, edited by J.P. Fouque, Les Houches Lectures (Kluwer, Dordrecht, 1999).[3] Juliette Billy, Vincent Josse, Zhanchun Zuo, Alain Bernard, Ben Hambrecht, Pierre Lugan, David Clement, Laurent Sanchez-Palencia, Philippe Bouyer & Alain Aspect. Direct observation of Anderson localization of matter-waves in a controlled disorder, Nature, 453, 891 (2008).Work published back to back with a related work in the Inguscio's group at Florence: G. Roati et al., Anderson localization of a non interacting Bose-Einstein Condensate, Nature, 453, 895 (2008).
Born in 1947, Alain Aspect studied at the Ecole Normale Supérieure de Cachan and Université d’Orsay. After a master thesis on holography and a three years teaching assignment in Cameroon, he started, in 1974, a series of experiments on the foundations of quantum mechanics. His “Experimental Tests of Bell’s Inequalities with Correlated Photons”, were the subject of his doctorate thesis presented in 1983. In 1983-86, with his student Philippe Grangier, he developed the first source of single photons and performed fundamental experiments on wave-particle duality of light. From 1985 to 1992 he worked with Claude Cohen-Tannoudji at the Laboratoire Kastler Brossel de l’ENS and Collège de France, on cooling atoms with lasers, in particular “cooling below the one photon recoil”. Since 1991, he is head of the Atom Optics group that he has established at the Institut d’Optique, now in Palaiseau. Recent scientific production concerns mainly Bose Einstein Condensates, Atom Lasers, Quantum Atom Optics with metastable Helium, Anderson localization of ultracold atoms. A CNRS senior scientist (”Directeur de recherches CNRS”) at Laboratoire Charles Fabry de l’Institut d’Optique, Alain Aspect is also a professor at Institut d’Optique and Ecole Polytechnique, Palaiseau. He is a member of the French Académie des Sciences, and of the Académie des Technologies, as well as of foreign academies (NAS, USA; OAW, Austria). He has received major awards, among them the OSA Max Born award (1999), the CNRS Gold Medal (2005), the Quantum Optics senior prize of the European Physical Society (2009), the Wolf prize in Physics (2010).
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