CQT Talk by Marie Piraud, Le laboratoire Charles Fabry de l'Institut d'Optique
Date/Time: Tuesday, 22 May at 4:00 pm
Venue: CQT Seminar Room, S15-03-15
Title: Matter wave transport and Anderson localization in anisotropic three-dimensional disorder
Abstract: We study theoretically quantum transport of matter waves in anisotropic three-dimensional disorder. We will first show that structured correlations can induce strong and unexpected effects, such as reversed anisotropies of scattering and diffusion, anisotropic suppression of the white-noise limit, and inversion of the transport anisotropy. We will also show that the localization threshold (mobility edge) is strongly affected by a disorder-induced shift of the energy states, which we calculate.
Our work is directly relevant to recent experiments of ultracold-matter waves in optical disorder:
- S. S. Kondov et al., Science 334, 66 (2011)
- F. Jendrzejewski et al., Nature Phys. (in press); arXiv:1108.0137v1 and implications on those experiments will be discussed. It also offers scope for further studies of anisotropy effects in other systems with controlled disorder, where counterparts of the discussed effects can be expected.
CQT Colloquium by Philippe Bouyer, Laboratoire Charles Fabry, France
Date/Time: Thursday, 24 May at 4:00 pm
Venue: CQT Seminar Room, S15-03-15
Title: Simulating quantum transport with atoms and light
Abstract: The transport of quantum particles in non ideal material 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 quantum systems are of fundamental interest as they show intriguing and non-intuitive phenomena that are not yet fully understood such as Anderson localization, percolation, disorder-driven quantum phase transitions and the corresponding Bose-glass or spin-glass phases. Understanding 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 revisit the problem of quantum conductivity and quantum transport under unique control possibilities. Dilute atomic Bose-Einstein condensates (BEC) and degenerate Fermi gases (DFG) are produced routinely taking advantage of the recent progress in cooling and trapping of neutral atoms. Transport has been widely investigated 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 observation of the Anderson Localization of a BEC in 1D and 3D,and the study of diffusion properties during matter-wave transport
CQT Public Lecture by Serge Haroche, Collège de France and Ecole Normale Supérieure, Paris
Date/Time: Friday, 25 May at 6:30 pm
Venue: NUS Block S16, Level 3, LT31 (Science Drive 2)
Title: Timing and taming light with atomic clocks
Abstract:
Norman Ramsey, who died last November, has revolutionized the measurement of time by inventing in the 1950’s the atomic interferometer named after him. This device, initially developed for high resolution spectroscopy, is used in atomic clocks which count the oscillations of electromagnetic fields with extraordinary precision. The most popular application of this “timing” of light in our everyday life is the Global Positioning System which exploits the signals sent by synchronized clocks embarked on a swarm of satellites orbiting the Earth. Atomic clocks are also used for very precise verifications of special and general relativity theory and for studying the possible time drifts of fundamental constants predicted by cosmological models. They are also employed in fundamental tests of quantum theory in which physicists juggle with photons trapped in cavities. Instead of “timing” the light, these experiments “tame” it by producing field states with unusual properties which could have applications for quantum information processing.
