Topological and unconventional quantum fluids

Imagine a super material. A synthetic material whose properties challenges our understanding of the fundamental forces in Nature. Synthetic quantum matter made out of ultra cold gases can be such a material. By trapping and preparing atoms with laser light we can dramatically alter the properties of the gas. Ultra cold gases, and their properties close to the absolute zero temperature, has therefore lead to major interdisciplinary research initiatives and insights, especially in synergy with condensed matter physics. Cold atom systems are now ready for emulating advanced many-body systems and topological states of matter where the presence of gauge fields is a key ingredient.

An apparent missing ingredient in the quantum gas tool box is the equivalent of orbital magnetism, which would allow for the simulation of a plethora of quantum phases. This proposal fills this gap. It uses the concept of optically induced artificial electromagnetism where the quantum gas is governed by an interacting gauge theory. This means there is a back-action between the matter field and the emergent gauge fields, which also results in new types of non-linear dynamics. The transport properties of such a gas are peculiar. For instance, the effective interaction strength between the atoms can depend on in which direction the gas moves; it is chiral. The time has now come to implement this new tool. With a new tool we can do new things.

One aspect of synthetic quantum matter is the prospect of having a topologically non-trivial material. Topology is the branch of Mathematics that deals with properties of geometric objects that do not change under smooth deformations, and therefore are also very robust against external perturbations such as defects, noise and external forces. There are many exciting phenomena associated with topological matter. Perhaps the most surprising, and possibly the most important, is the existence of metallic edge states in a material that is insulating in the bulk. In other words, the properties of the edge of the system characterises also the bulk properties. The physics of the edge states can be very exotic. There can for instance be excitations, or quasi particles, which do not behave like fermions or bosons -- but as something in between. This property, together with the extreme robustness against imperfections and noise, also makes topological matter a promising candidate for building an error-free quantum computer which has all the potential to revolutionise modern technology and our society.

With the combination of nonlinear synthetic gauge fields and charge neutral ultra cold quantum gases, we have at hand a new type of material described by an interacting gauge theory. What are the properties of such a material? What can it be used for? This is the main motivation of the project.

This research is purely curiosity driven. Quantum fluids governed by an interacting gauge theory is uncharted territory. We have a new tool at hand, and will study with it a range of new phenomena related to magnetism and gauge theories. It will enhance our understanding of matter at the most fundamental level, where the main tool will be ultracold quantum gases, synthetic gauge fields and strongly correlated many-body systems. The core theme is to address fundamental open questions, create novel quantum-many body systems and seek applications beyond the realm of quantum gases.

The research proposal aims to provide a significant contribution to this knowledge acquisition. This is the main driving force behind the entire project, and is the area in which we envisage the biggest impact will be.

The results will be disseminated at high profile international conferences such as for instance the the ICAP and the DAMOP conferences. The project aims to publish in leading journals such as Nature, Science and Physical Review Letters, but also longer review style publications intended for a more general audience. The project will also have a web page in the format of a blog which will be aimed at a general audience where the latest research news from the project are explained and discussed in a non-technical language.

The research will enhance the pool of scientific talent in the UK. The project will provide direct training for one RA. It will be an integral part of the Scottish Universities Physics Alliance, SUPA (www.supa.ac.uk), the Institute of Photonics and Quantum Science (IPaQS) at Heriot-Watt University, and also the International Max Planck Partnership (IMPP). In addition there will be a close collaboration with the EPSRC funded Scottish Doctoral Training Centre in condensed matter (http://cm-dtc.supa.ac.uk/) where we expect at least two PhD students to be involved in the proposal's research topic. This and SUPA will provide international-level training in the core discipline of condensed matter physics. The project team members will be able to attend courses and events run by the Doctoral Training Centre and SUPA, and benefit from the internationally leading graduate programme. As such, the project will foster the scientific excellence of RAs and PhD students on a broad basis and not only restricted to the project itself.

There is no short term economic impact of the current proposal. Long term economic impact (twenty years or longer), we can only speculate about. It is, however, not difficult to envisage a number of potential technological applications which would stem from improvements in our ability to understand, engineer and control quantum systems and the various states of matter. Technologies such as quantum metrology (e.g. atomic clocks), quantum cryptography and superconductivity are concepts which already have a commercial impact, and rely critically on our ability to control systems at the quantum level. As such, a future major economic impact could well come from new exotic artificial magnetic materials, one of the corner stones of the proposal.

We envisage the proposal forming a key ingredient in the foundations of future quantum technologies. We do not know what such quantum technologies will bring us, the quantum computer is the most famous candidate, but it is certainly not the only possibility. We can however be sure that in a not so distant future quantum control will be required in order to sustain the current technological evolution.

To ensure that the project will be part of such a process we will engage in collaborations with both experimental and theoretical groups, and rely on an extensive international network of collaborators. This will be in the form of publications, conference attendance and longer research visits to other research groups working on quantum control of matter.