Rydberg soft matter

The world around us is in a state of constant change. Physicists refer to this as being "far-from-equilibrium". Far-from-equilibrium systems are common throughout nature, and non-equilibrium dynamics is encountered in problems as distinct and varied as biological self-assembly and the behaviour of financial markets. Remarkably, even though physics is a very mature and advanced field, it has comparatively little to say about systems far-from-equilibrium. In this proposal we will help to fill this void by exploiting atomic systems where we have complete control over interparticle interactions, but which also display a remarkable richness in their collective and far-from-equilibrium behaviour. Our atomic system is based on individual atoms where we can control the interactions using laser pulses to promote the atoms to highly excited states known as Rydberg states. An ensemble of atoms excited to Rydberg states can display complex spatial and temporal dynamics that are analogous in many ways to soft matter systems such as colloids or glasses. Due the capability to control microscopic interactions, this "Rydberg soft matter" offers the possibility to gain new insight into how the microscopics determine the collective macroscopic behaviour, both in dynamics and structure. A second special feature of Rydbergs is the ability to control the relative importance of quantum effects. By studying small systems where quantum fluctuations dominate we can probe the boundary between the quantum and classical worlds, and study quantum triggers of classical events which relate to fundamental questions such as macroscopic entanglement and the quantum measurement problem. Such systems also offer considerable potential for applications in the emerging area of quantum technology.

Rydberg soft matter offers an unprecedented opportunity to break new ground in some of the most flourishing areas of current research. Significant progress, however, demands a close interplay between theory and experiment. To address this we have assembled an interdisciplinary team of theorists and experimentalists, all based in the UK, but with a combined expertise that is unique worldwide. We will begin by developing the microscopic theory which is relatively straightforward and easily tested by experiment. The challenge comes in extending the microscopic theory to treat many particles. At this stage we need experiments to validate the approximations and guide the direction of the theoretical development. Finally, the theory will guide the experiments to answer fundamental questions and develop potential applications. The novelty of Rydberg soft matter, the close interlinking of theory and experiment, and the unique skill set of the investigators will allow us to pioneer new directions in physics that address key questions both fundamental and applied.

1. Academic impact

The goal is to make a major advance in our understanding of systems far-from equilibrium and hence directly address one of the most important scientific questions of today. Advances in this area will enhance our understanding and ability to control (a) the properties of complex materials, (b) the dynamics of nanoscale assembly, and (c) the behaviour and interaction of macromolecules in biology.

2. Technological impact

The experimental programme will lead to spin-off applications particularly in the area of quantum technology. One promising direction is the possibility to use Rydberg soft matter systems to realise highly efficient single photon detectors. Such detectors could give both time and spatial information similar to a phosphor screen but with much higher quantum efficiency.

3. Training

The proposal will produce highly trained personnel at all levels from undergraduate to post-graduate and post-doctoral. The close synergy between experiment and theory and the interdisciplinary nature of the project will result in a broad training that will equip all personnel with a unique and special skill base.

4. Outreach

The researchers involved have a strong track record of outreach in local schools, hosting school visits (for the latest activity, see e.g. http://www.jqc.org.uk/news/article/primary-school-visit/2014-05-01/12663), and public lectures. We plan to continue these activities with aim of enhancing the profile of science in our respective regions.