Abstract

Quantum dynamics is one of the most challenging theoretical problems in science, due to the underlying exponential complexity. The environmental isolation and simplicity of ultra-cold gases allows theoretical predictions to be tested with unprecedented accuracy. In this talk, the question of quantum mixtures is investigated. Two theoretical methods will be treated. The first is an exact first-principles approach, using the positive P-representation to investigate the transport and quantum entanglement of a dilute quantum impurity in a host BEC . The second is an approximate method especially useful on long time-scales. In this approach the hydrodynamic equations are quantized and solved using a truncated Wigner method. This is applied to 1D interferometry and transport in Rubidium isotopic mixtures. It explains how a combination of quantum transport and phase-diffusion results in fringe decoherence in agreement with experiment.