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Theme 2a. Quantum Fluids and Gases (QFG)

 

Members of the Quantum Fluids and Gases Theme

 

Theme Leader: Joachim Brand

Investigators: Rob Ballagh, Blair Blakie, Joshua Bodyfelt, Ashton Bradley, Howard Carmichael, Oleksandr Fialko, Sergej Flach, Maarten Hoogerland, David Hutchinson, Niels Kjærgaard, Scott Parkins, Uli Zuelicke

 

Project (QF1) Spin Fluids

The spin fluids project aims at manipulating and probing ultra-cold atomic gases with multiple components and spin degrees of freedom.

 

i) Multicomponent gases in designer potentials: We will study the dynamics of a Bose condensate residing in a bath of thermal atoms. Our toolbox allows us to set up the bath with atoms in identical or different spin states, or even a different atomic species. By using Feshbach resonances we will be able to tune the interactions between the system components while our steerable optical tweezers system will allow us to ‘paint’ arbitrary confinement potentials for the atoms, i.e. with box-like confinement.

ii) Detection of correlations: By using our capability to precisely engineer internal state distributions, we will extend our correlation studies to include entanglement of atomic spins.

 

Project (QF2) Quantum Emulation and Simulation

 

We will analyse the use of ultra-cold atomic gases as versatile and configurable quantum systems that can be engineered to emulate physical processes of importance or practical interest that are otherwise hardly accessible. The ultra-cold gas can then be used as an analog computer to simulate the original quantum system. This theory project combines the expertise of researchers from MU, VUW, UoO in the fields of nonlinear waves, functional nano structures, stochastic field simulation, and implementation of ultra cold gas experiments. As a team, we want to consider the engineering of quantum gases beyond the scope of project (QF1) and anticipate and prepare the next generation of quantum gas experiments aimed at emulating exotic material properties used in spintronic devices and simulating important and poorly understood processes relevant for the evolution of the early universe and the properties of neutron stars.

i) Quantum simulation of relativistic field models. Prior work and our own recent results suggest that coupled two-component Bose-Einstein condensates can emulate the dynamical behaviour of relativistic quantum field theories that are relevant, e.g., for understanding cosmic inflation. We will characterise the low-energy excitation spectrum of this class of models including the soliton excitations.

 ii) Emulating the inside of a neutron star. Fermi superfluids with very strong inter-particle interactions occur below the crust of neutron stars and in heavy ion collisions. We will revisit the influence of strong quantum fluctuations on soliton excitation in a quantum fluid based on perturbative and stochastic techniques in comparison to exactly solvable one-dimensional models.

 iii) Quantum fluid dynamics. Our recent work on turbulence in scalar condensates has opened new directions in the quantitative study of quantum turbulence.

 

 

Project (QF3) Atomtronic materials and novel probes

Atomtronics is a rapidly emerging area in which devices analogous to those operating on electrons (e.g. circuits) and photons (e.g. interferometers) are made using ultra-cold atoms. The modelling of these systems presents a challenge for established theoretical techniques because the situations are dynamical (not in steady-state) and consist of both coherent and superfluid dynamics. The work in this project is initially theoretical, but will focus on devices that could be implemented using the experimental techniques developed in (QF1) and (QF4).

i) Novel materials for thermal atomtronic devices. Understanding, controlling, and manipulating flows of heat, entropy, and particle currents in ultra-cold atom systems enables us to create novel devices that fulfil tasks from the analogues of thermal valves or transistors to complete heat engines.

ii) Light scattering as probe for quantum correlations. The theory of light scattering from single atoms is well understood, but in ultra cold atom systems multi-atom quantum coherences may contribute significantly to the system properties.

ii) Controlling spin-orbit coupled Bose gases. We will develop a comprehensive theory of soliton and vortex coupled magnetisation dynamics and orbital motion with the purpose of guiding future experimental development towards the control of the spin degree of freedom for atom-spintronic devices.


 

Project (QF4) Disordered Quantum Matter

The exquisite control of experimental parameters in ultra-cold atom experiments has made it possible to scrutinise the properties of current flow, or transport, in the presence of disorder and interactions in completely new ways and thus has opened new opportunities and challenges for experiment and theory. The project seeks to contribute to resolving the big question of how many-body interactions affect the localisation effects.

We will investigate:

i) Dependence of Anderson localisation on arbitrary, tuneable interactions.

ii) Flat bands. Using custom designed potentials we will implement optical lattices with flat bands in the dispersion.