Research

Our research focuses on Bose-Einstein condensate dynamics in arbitrary optical potentials. In late 2006 we made the first observation of the a.c. and d.c. Josephson effects in a double-well configuration in a BEC You can read an account of this experiment here. Our system traps and cools 87Rb atoms in a magneto-optical trap (MOT). The atoms are then transported to a Quadrupole-Ioffe configuration (QUIC) magnetic trap, where they are evaporatively-cooled through the critical temperature to form a Bose-Einstein condensate (BEC) of about 105 atoms.

We can add a potential barrier (or well) to the trap by applying an appropriately detuned laser beam, shaped as a thin sheet. This creates a double-well configuration. By shifting the beam away from the magnetic trap center, we can control the relative volume of the two wells, hence the chemical potential of the two condensates. The power and waist size of the laser control the amount of coupling between the condensates.

The BEC is investigated by absorption or phase-contrast imaging. We use an NA 0.5, 8mm focal length lens to achieve an observed optical resolution of 1.2 μm. This is the same order of magnitude of the potential barrier width, or tunneling, length scale.