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Content archived on 2024-05-29

Quantum phases and disorder effects in ultra-cold quantum gases

Final Activity Report Summary - QPDEUGAS (Quantum phases and disorder effects in ultracold quantum gases)

Ultracold bosonic and fermionic quantum gases are versatile and robust systems for probing fundamental condensed-matter physics problems as well as finding applications in quantum optics and quantum information processing and understanding atomic and molecular physics. Storing such ultracold quantum gases in artificial periodic potentials of light has opened innovative manipulation and control possibilities, in many cases creating structures far beyond those currently achievable in typical condensed-matter physics systems. Amazingly, strong correlation effects can be observed in dilute atomic gases despite the densities of the particles in the trapping potentials being more than seven orders of magnitude less than that of the air surrounding us.

Ultracold quantum gases in optical lattices can in fact be considered as quantum simulators, as Richard P. Feynman originally conceived for a quantum computer: a powerful simulator in which a highly controllable quantum system can be used to simulate the dynamical behaviour of another complex quantum systems. Thus theoretical and experimental investigations of ultracold atoms in optical lattices open the door to a wide interdisciplinary field of physics ranging from non-linear dynamics to strongly correlated quantum phases and quantum information processing which will provide our Community with many research highlights throughout the coming years and has already deserved a Nobel prize in 1997. The research project dealt with theoretical investigation of novel quantum phases, disorder effects and transport in ultracold bosonic and fermionic gases with low-dimensionality. Its aim has been to advance our understanding of complex quantum matter under extreme conditions.

Concerning the effects of disorder, the innovative aspect of the Project has been to develop a new approach, by combining different techniques of condesed-matter physics applied to treat strongly correlated low-dimensional systems, to specific systems of atomic physics, i.e. ultracold bosonic species in optical lattices. The phase diagram of interacting bosons in a quasi periodic optical lattice was determined and fully characterised by the calculation of measurable physical quantities. As for the analysis of transport in Bose Einstein condensates we have been proposing a new probe for superfluidity based on quantum stirring ('spooning of a condensate').

We are aware of the fact that the results of the present project represent a significant contribution to clarify the nature of the ground state of quantum gases to go beyond the current state of the art and could represent a reference point for experimentalists in the field. Exploring novel quantum phases and disorder effects is relevant to the development of future atomtronic quantum devices as well as quantum computation and quantum information schemes, design of experiments for fundamental physics such as tests of general relativity, and can be useful to understand condensed matter analogs. Knowledge and technological developments are hard to estimate here and their potential has legitimated all the current experimental efforts to scale Bose-Einstein condensates down onto a chip.