Strontium Rydberg project
Experiment: Alistair Bounds, Dan Sadler, Danielle Boddy, Liz Bridge, Charles Adams and Matthew Jones
Theory: Christophe Vaillant, Robert Potvliege
Past Members: James Millen, Graham Lochead
Laser cooling and laser spectroscopy are powerful techniques for controlling the motion and quantum state of individual atoms. In this project we aim to extend this level of control to the interactions between the atoms. By exciting laser-cooled strontium atoms to a very high lying electronic energy state - known as a Rydberg state, we can switch on strong, long-range van der Waals interactions between the atoms, which completely dominate the behaviour of the atom cloud. Uniquely, our experiment uses strontium atoms, which also have a second valence elctron that can be used to probe and manipulate the Rydberg gas. So far, we have shown that this can provide information on collisions that can transfer atoms from one Rydberg state to another, with very high temporal resolution. We have also extended these techniques to provide spatial information, enabling us to probe spatial correlations in this strongly interacting system.
Our experiments are supported by detailed calculations of the properties of interacting strontium Rydberg atoms carried out by Christophe Vaillant and Robert Potvliege.
Current Research Directions

The strong interactions between Rydberg atoms lead to novel strongly correlated phases. A carefully tailored, strong coupling to the Rydberg state leads to the dynamical formation of Rydberg crystals, where the interactions lead to long-range order in the spatial distribution of rydberg atoms. Conversely, using a weaker off-resonant coupling we can map these spatial correlations onto a Bose-Einstein condensate, raising the possibility of observing a ``supersolid'' state. More details can be found in our article for non-specialists (right), published in International Innovation.

This research is supported by EPSRC grant J007021/1

Recent results In our latest paper, we demonstrate a new method for measuring the spatial distribution of Rydberg atoms with single-atom sensitivity. With improved resolution, this method could be used to observe a Rydberg crystal.

Atomic clocks based on an extremely narrow optical transition in strontium are currently leading the field in stability and accuracy, enabling frequency measurements at the 10-18 level. In an ongoing collaboration with the group of Thomas Pohl at the Max Planck Institute for Complex Systems in Dresden, we are investigating the use of Rydberg states to improve the performance of the clock even further.

This work is supported by the EU STREP HAIRS, a network of researchers from Durham, Nottingham, Tubingen, Dresden and Palaiseau with the aim of using these techniques to create a hybrid quantum system of atoms and superconducting circuits.

Recent results The figure on the right is from our preprint where we propose to create very strongly squeezed states in a lattice clock using Rydberg dressing, with implications for quantum-enhanced frequency metrology.

Latest graph:

5th July 2013: A fluorescence image of atoms cooled on the narrow intercombination line at 689nm. This "red MOT" is three orders of magnitude colder than the "blue MOT" that we have been using previously. We are now optimising the density and temperature ready for Rydberg experiments.

Content © Matthew Jones, Durham University 2007