thesis

Rydberg-Stark deceleration and trapping of helium atoms above electrical transmission-lines

Abstract

The experimental realisation of a set of surface-based devices for controlling the positions and velocities of Rydberg atoms initially travelling in pulsed supersonic beams is described. The unique aspect of these devices is that they are based on the geometry of two-dimensional electrical transmission-lines and are therefore suited to integration with chip-based microwave circuits to realise a complete Rydberg laboratory on a chip. Such a chip-based laboratory could be exploited in hybrid approaches to quantum information processing, and for studies of collisions and decay processes of highly excited atoms and molecules. The devices operate through the generation of inhomogeneous electric fields and take advantage of the large electric dipole moments associated with high Rydberg states to exert forces on the atoms. In the experiments, helium atoms in Rydberg-Stark states with principal quantum numbers ranging from 48 to 52 and electric dipole moments of 10000 D are employed. The devices developed include electrostatic guides which permitted control over the transverse motion of beams of atoms. These were used to transport samples, initially travelling at 1950 m/s and deflect them away from their initial axis of propagation. The guided atoms were detected by pulsed electric field ionisation. To control the longitudinal motion of the samples, the transmission-lines were modified to permit the generation of sets of continuously moving electric traps. The resulting transmission-line decelerators were then employed to guide, accelerate and decelerate atoms trapped in three-dimensions. Accelerations up to 2.3 x 10^{7} m/s^{2} were applied to decelerate samples from 2000 m/s to zero-velocity in the laboratory-fixed frame of reference, leading to the removal of 80 meV of kinetic energy, the largest achieved in any Stark decelerator to date. The decelerated atoms were trapped in stationary electric traps and detected in situ. The phase-space acceptances of the decelerators were calculated to characterise the effects of acceleration and deceleration on the trapped atoms. The results of the calculations were employed in the interpretation of the experimental data, and to identify effects of collisions and blackbody transitions

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