Michael Brownnutt

This thesis was based in NPL. 

Click here to download thesis: 88Sr+ ion trapping techniques and technologies for QIP

Title: ⁸⁸Sr⁺ ion trapping techniques and technologies for quantum information processing

Abstract: 

This thesis describes techniques used in trapping and cooling a single ⁸⁸Sr⁺ ion. It also presents the development of a novel technological approach for fabricating a scalable trapped-ion quantum information processor.

A single ⁸⁸Sr⁺ ion is loaded into a radio-frequency endcap trap. To facilitate this a clean, efficient method of photoionising Sr via a two-step resonant process has been developed, using all diode-based laser systems. This method of trap loading is quantitatively compared to the previously-used electron-bombardment loading method, and shown to reduce the Sr vapour pressure required to load by four orders of magnitude. It also provides more than an order of magnitude reduction in the day-to-day variation of the voltages required to compensate micromotion.

A single trapped ⁸⁸Sr⁺ ion is then cooled to the zero point of its axial motion. A ground-state occupation probability of 98.6(8)% was achieved using resolved-sideband laser cooling on the 674 nm ²S_1/2→²D_5/2 quadrupole transition. The ion's heating rate was measured to be 0.054(4) quanta/ms, implying a spectral density of electric-field noise comparable to the other values reported in the literature.

Finally a design for a novel microfabricated ion trap is proposed. By using a process based on planar silica-on-silicon techniques, the trap electrodes are made of gold-coated silica and are spaced by highly-doped silicon in a monolithic structure. The trapping potential is modelled and the operating parameters required to achieve experimentally useful motional frequencies are calculated. Practical concerns — including RF heating of the substrate, and electrical- and mechanical- breakdown — are investigated and are not expected to limit the operation of the trap. Progress towards the fabrication of such a trap is also presented.

Issue Date: September 2007

Supervisor: Thompson, Richard

                     Sinclair, Alastair (NPL)

Item Type:  Physics PhD Thesis