Department of Physics and Theoretical Physics, **Machine ** CM

The Faculties

**Atom Optics**

Atom optics is the study of the wave nature of atoms. According to quantum mechanics matter has a dual particle-wave nature. We usually think of atoms as particles, but sometimes their behaviour can only be understood if they are modelled as waves. A specifically wave-like phenomenon is diffraction. The focus of this project is on atom diffraction from gratings made of light. There is an ongoing experimental atom optics program at ANU, in both the Faculties and the Research School of Physical Sciences and Engineering. Apart from its intrinsic interest this project supports that program through modelling. Project r71 explored atom waveguides. In particular we investigated the bound states that occur in non-uniform waveguides.

**What are the basic questions addressed?**

Can a supercomputer model quantitatively reproduce experimental results? If so, under what conditions will the ANU atom diffraction experiment perform optimally?

**What are the results to date and the future of the work?**

Excellent agreement has been obtained between the computer model and preliminary ANU experiments. This has facilitated planning of future experiments. Presently the atoms are modelled by only two atomic energy levels, in both this model and analytical ones. From experiments it has become clear that more levels are required. This is the focus of work for 1995.

**What computational techniques are used and why is a supercomputer
required?**

The modelling of atom diffraction requires solution of the Schrodinger equation in two spatial dimensions and time. A standard split operator/FFT technique is used. The degree of realism we are demanding from our model requires us to solve a system of partial differential equations, one equation for each atomic energy level. This, together with the need to scan parameter space, requires supercomputing to be feasible.

**Publications**

*Bound states of two-dimensional non-uniform waveguides*, M Andrews
and C Savage, Physical Review A, **50**, 4335 (1994).