Coherent control of spin systems for quantum information processing

Thesis

Over the last few years, the GRAPE algorithm has become of central importance in the development of general purpose control sequences for several branches of Nuclear Magnetic Resonance. In this thesis, the application of the GRAPE algorithm to quantum information processing tasks is considered. First the theory underlying the algorithm is reviewed in detail, then a number of extensions and improvements to the core technique are developed. An implementation of the GRAPE algorithm using GPUs is presented and compared with a standard CPU based implementation.

A variety of experimental results are presented covering many different aspects of the practical use of GRAPE. This includes an evaluation of some of the errors that can affect the performance of GRAPE sequences in real experiments, and their relative importance. The strengths and weaknesses of GRAPE compared to the other possible techniques are assessed, and some suggestions made regarding potential developments in this direction.

Pseudo-pure states are a crucial component of any NMR based quantum computer, but many current methods for preparing them sacrifice purity in exchange for simplicity in the preparation sequence. This thesis also presents a new method for robustly generating pseudo-pure states with the maximum possible purity.

Authors: Rowland, B; Ben Rowland

• Publication date: 2012
• DOI: 10.5287/ora-aejxxg4k6
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: spin simulation; GRAPE algorithm; NMR
• Subjects: Atomic and laser physics