Time-averaged potentials

We have developed a new apparatus that produces 87Rb Bose-Einstein condensates of 1× 106 atoms. We then transfer the condensate onto a "light sheet" potential using 1064 nm light, which traps the atoms onto a plane. Using another a rapidly scanned laser beam (1064 nm) in the vertical direction, we can "paint" a variety of traps for the atoms. The beam is scanned using a 2D acousto-optical deflector (2D-AOD), and is scanned very a high rate (>5 KHz) so the atoms "see" the time-averaged potential. Using a feedback technique, which uses the distribution of atoms as a probe, we can compensate for intensity variations, and make ultra-smooth homogeneous potentials.

BEC in various time-averaged traps including coupled "dumbell" reservoirs, and lattices with 3, 4 and 6 wells. Each image is 200 µm and 200 µm.

We are particularly interested in

- Superfluid dynamics in ring potentials.

- Sound wave (phonon) excitations in time-averaged potentials.

- Waveguides for BEC interferometry.

- Superfluid convection and heat transport in coupled reservoirs.

For more information contact Dr Mark Baker

BEC of ~ 150,000 atoms in a ring trap, of 140 µm diameter.

BEC of 150,000 atoms released into a 300 µm diameter waveguide, over 100 ms. Each frame is separated by 2.5 ms.

ARC Discovery Projects: Spin vortex dynamics in a ferromagnetic superfluid (2020-2023)

Magnetic spin vortices are stable whirlpool-like objects that can spontaneously form when magnetic materials are rapidly cooled. This project aims to understand and manipulate spin vortices in a magnetic quantum fluid, one of the cleanest and most controllable magnetic systems. The significance is that spin vortices are potentially fundamental elements of future electronic technologies for advanced storage and logic. The expected outcomes are the ability to create spin vortices on demand, and the characterisation of their suitability for future applications.

ARC Discovery Projects: Riding a quantum wave: transport and flow of atomic quantum fluids (2015–2018)

Abstract: In our lab, we use lasers and magnetic fields to cool tiny samples of millions of atoms to temperatures a few billionths of a degree above absolute zero. At such cold temperatures they form a superfluid known as a Bose-Einstein condensate, that flows with zero viscosity. Using tailored light fields to trap and guide the atoms, we will build rudimentary atomic circuits, and coax the superfluid to flow through a channel between two reservoirs, firstly with thermodynamic gradients, and secondly by building a quantum pump.

Gauthier Guillaume et al, 2019
Physical Review Letters, 123, 26

We experimentally realize a highly tunable superfluid oscillator circuit in a quantum gas of ultracold atoms and develop and verify a simple lumped-element description of this circuit.

Gauthier Guillaume et al, 2019
Science, 364, 6447, pp. 1264-1267

Adding energy to a system through transient stirring usually leads to more disorder. In contrast, point-like vortices in a bounded two-dimensional fluid are predicted to reorder above a certain energy, forming persistent vortex clusters.

Rapidly scanning magnetic and optical dipole traps have been widely utilized to form time-averaged potentials for ultracold quantum gas experiments.

Rubinsztein-Dunlop Halina et al, 2017
Journal of Optics, 19, 1, pp. 13001

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge.

The development of novel trapping potentials for degenerate quantum gases has been an important factor driving experimental progress in the field. The introduction of spatial light modulators (SLMs) into quantum gas laboratories means that a range of configurable geometries are now possible.

Interferometric measurements with matter waves are established techniques for sensitive gravimetry, rotation sensing, and measurement of surface interactions, but compact interferometers will require techniques based on trapped geometries.

Prof Halina Rubinsztein-Dunlop
Chief Investigator, Professor
Chief Investigator, Research Fellow
Matthew Davis
Chief Investigator, Professor
Tyler Neely
ARC Future Fellow / Senior Lecturer