MvL-Kolloquium: Prof. Dr. Alain Aspect

In the early 1980's, Feynman realized that many-body entangled systems pose an insurmountable challenge to classical computers and suggested that a promising way to attack the problem is to simulate the situation with an equivalent quantum system. Since the early 2000's, ultra-cold atoms have been found an excellent system to realize Feynman's program and realize quantum simulators of difficult condensed matter problems, where many electrons are entangled. One can cite the Mott insulator to supraconductor transition in a lattice, or the BEC-BCS transition, to name only a few. We study the problem of quantum particles in a disordered potential and in particular the celebrated Anderson localization phenomenon, i.e. the total suppression of conductivity beyond a certain level of disorder, a phenomenon impossible to understand in a classical framework. Our experiments use atomic Bose-Einstein condensates in optical disordered potentials based on laser speckle. I will describe the Anderson localization phenomenon, present some experimental results that shed new light on strong and weak localization, and evoke the still open problems.