Coherent excitation of ultracold atoms between ground and Rydberg states

Abstract

This thesis describes the development of an experiment to study coherent population transfer between ground states, and between ground and Rydberg states, in ultracold atoms.

In order to study coherent transfer between hyperfine ground states a pair of phase stable Raman beams is required. Both beams are derived from a single master laser before being spatially separated into individual components using a novel Faraday filtering technique. The frequency dependent Faraday effect in an isotopically pure thermal vapour is exploited to rotate the plane of polarisation of each Raman component such that they may be separated using a polarising beam splitter. The Raman beams are applied to a sample of ultracold atoms and evidence of coherent population transfer is observed.

Rydberg states offer an ideal tool for electrometry; the electric field induced Rydberg energy level shift scales with the seventh power of the principle quantum number. Electromagnetically induced transparency (EIT) is used to map Rydberg energy level shifts onto a ground state transition. EIT in a thermal vapour cell also provides a novel method of stabilising the Rydberg coupling laser. The Rydberg energy level shift is highly sensitive to the electric field produced by adsorbates bonded to a nearby dielectric surface. These effects are found to be time dependent and can be eliminated if the electric field is applied transiently. The measured electric field is compared to that calculated by numerical solution of Laplace's equation; the bulk dielectric is found to have a strong effect on the local electric field experienced by the atoms.

The exaggerated properties of Rydberg states make these systems ideal for quantum information processing and precision electrometry.