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Ultracold Atoms

The advent of laser cooling some three decades ago produced trapped atomic gases at astoundingly low(sub-milli-Kelvin) temperatures, initiating the field of ultra-cold atomic physics. This field, recognized by two separate Nobel Prizes, has remained at the cutting-edge of physics research because these degenerate gases are pristine systems for exploring fundamental quantum phenomena.

for an introduction

A key factor in the progress made with these systems is the detailed understanding of atomic interactions and how they can be controlled. For example, using so-called Feshbach resonances, the interactions between atoms can be varied from being attractive to repulsive by adjusting the strength of an external magnetic field. This provides a unique control parameter to explore paradigmatic condensed matter physics such as superconductivity in strongly interacting gases. However, it is not possible to directly calculate atomic interaction potentials from first principles, and current understanding is provided by theoretical models that have been determined (and continue to be optimized) by comparison to experimental measurements.

Laser Based Collider for Ultracold atoms

We are presently developing a novel collider to perform high precision atomic physics measurements. Like the high-energy colliders used in particle physics, our apparatus will smash together bunches of atoms and analyze the spatial distribution of the scattered debris. However, our collider will operate
in a regime of extreme contrast: it will use samples of atoms at nano-Kelvin temperatures accelerated to pedestrian velocities of up to a meter per second. The full execution of this collider utilizes collaborations with theorists who have developed state-of-the-art calculations to extract key information from the experimental scattering patterns.
This collider extends our previous magnetic collider experiments.

Achieved Milestones towards our research goal

Improved, reliable production of degenerate Fermi gas of K-40 (May 2014)

Image shows > 500,000 K-40 atoms at a temperature of 0.6 TF .

Quadruple BECs (May 2014)

Observation of the mixed spin channel Feshbach resonance near 9.1 G in Rb-87(March 2014)

Steerable optical tweezers (Jan 2014)


Click above to download high res image of our steerable tweezer system
Below: Splitting of ultracold atomic clouds

BECs in configurable time-averaged double-wells

Winding spin waves in a gas of ultracold Rubidium atoms

Image shows time-of-flight images of spin up and spin down atoms when separated by a Stern-Gerlach field after winding up a spin wave with a microwave field

Dispersive probing of Rabi oscillations on between the stretched hyperfine states of Rb87

New optical layout for dual species MOT

Homebuilt motorized rotation mounts for wave plates

Click here to see animation

Dispersive Interrogation of an ultracold atomic cloud during rf evaporation (October 2012)

We have used nondestructive laser probing to follow the central density evolution of a trapped atomic cloud during forced evaporative cooling. This was achieved in a heterodyne dispersive detection scheme. We propose to use this as a precursor measurement for predicting the atom number subsequent to evaporation and provide a simple experimental demonstration of the principle leading to a conditional reduction of classical number fluctuations.

Dispersive probing of Rb87 in a MOT using phase modulation spectroscopy (May 2012)

Making and Probing BECs with a single diode laser (February 2012)

Potassium MOT up running (January 2012)

Toptica DL Pro laser up running (October 2011)

We have received and installed our new commercial 780 nm diode laser.
This laser is intended to form the back bone in a new architecture for
cooling, repumper, pumper, and probe light in our experiment.

Making Movies (September 2011)

Click to watch

Laser based collider for ultracold rubidium atoms

First scattering observed in the optical collider (29 August 2011)

One of the first images of rubidium-87 atoms undergoing s-wave scattering in the new optical collider.

Crossed dipole trap aligned (?? August 2011)

Bose-Einstein condensate of 87Rb (23 July 2011)

One of the early shots of a Rubidium-87 BEC in the |2,2> state. Subsequently, we managed to make bigger, more pure BECs:

The cloud all the way on the left is a purely thermal cloud. A BEC emerges in the next cloud on the right. As we cool further, the thermal atoms disappear and we are left with an almost pure BEC.