Simulating transport with atoms and light
Résumé
The transport of quantum particles in non ideal mate- rial media (eg the conduction of electrons in an imperfect crystal) is strongly affected by scattering from impurities of the medium. Even for a weak disorder, semi-classical theories, such as those based on the Boltzmann equation for matter-waves scattering from the impurities, often fail to describe transport properties and full quantum approaches are necessary. The properties of the quan- tum systems are of fundamental interest as they show intriguing and non-intuitive phenomena that are not yet fully understood such as Anderson localization, percola- tion, disorder-driven quantum phase transitions and the corresponding Bose-glass or spin-glass phases. Under- standing quantum transport in amorphous solids is one of the main issues in this context, related to electric and thermal conductivities. Ultracold atomic gases can now be considered to re- visit the problem of quantum conductivity and quan- tum transport under unique control possibilities. Dilute atomic Bose-Einstein condensates (BEC) and degener- ate Fermi gases (DFG) are produced routinely taking advantage of the recent progress in cooling and trap- ping of neutral atoms. Transport has been widely in- vestigated in controlled potentials with no defects, for instance periodic potentials (optical lattices). Controlled disordered potentials can also be produced with various techniques such as the use of magnetic traps designed on atomic chips with rough wires, the use of localized impurity atoms, the use of radio-frequency fields or the use of optical potentials. This recently lead to the ob- servation of the Anderson Localisation of a BEC and the measurement of the diffusion coefficient of a 2D gaz in the presence of disorder.
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