I am currently in the middle of my Ph.D. programme here at the University of Queensland. I am working in the ARC Centre of Excellence for Quantum-Atom Optics (ACQAO). My current and previous research all lie in the domain of theoretical atom otpics, mainly performing simulations of Bose-Einstein condensate systems. My first work in this area was on feedback schemes for Bose-Einstein condensates. The idea was to measure properties of the condensate (such as its mean position) and feedback to the potential in order to stabilise it and reduce the total energy. We modelled the system with the G.P.E. and ignored the quantum effects of measurement. Since then I have focussed less on semi-classical applications to condensates and more on interesting quantum effects. In my honours thesis I investigated a way of detecting the quantum state of an atom laser. The scheme presented investigates the quantum information stored in the side-bands of an atom laser. My Ph.D. work has predominately dealt with condensates in optical lattices. Dynamical instabilities in optical lattices lead to two interesting effects: the first is spontaneous heating of the condesate, the second is production of entanglement through a four-wave mixing process. Neither of these effects are described adequately by semi-classical theories such as the G.P.E. I have applied quantum models (in particular the truncated Wigner approximation) to simulate these systems. Most recently I have been investigating the possibility of generating and measuring entanglement in atomic systems by the above mentioned process. Atomic four-wave mixing allows us to generate this entanglement, the difficulty is in creating a realistic scheme for measuring the entanglement. For now there are some movies I wanted to post. They are simulations of BEC's in an optical lattice using the truncated Wigner method. The movies show 2D momentum space and evolve in time. Dynamical instabilities are observed. The first shows the results of a BEC instantly loaded at the band edge of the lattice. Oscillations are seen at short times, but damp out as a number of complicated modes are populated. Eventually it thermalises. In the second movie the BEC is loaded at the edge of the lowest Bloch band. The conditions for energy matching are seen in the inner ring. The third shows the same for the edge of the first excited band. Note energy matching conditions are much narrower and form a complicated pattern. For comparison sake, I have included simulations of collsions in free space, where energy matching occurs in the usual ring. |