Novel precision control techniques in a trapped Yb+ ion implementation

Abstract

Precise control of quantum systems is vital to scientific and technological progress, including the realisation of quantum computation and simulation, record-breaking timekeeping and positioning applications. Control of quantum systems is hampered by the effects of random environmental or hardware noise, which leads to unknown deviations from the system's desired evolution. This thesis presents a set of interaction-focussed methods for improving precision control, tailored to the problems of quantum error suppression and stabilisation of oscillators, which share a common basic structure. These methods are based on a theoretical framework called the filter-transfer function formalism, which expresses the convolution of user-applied control and random noise in the language of spectral filtering. This powerful and accessible approach is experimentally verified in this thesis, and is used to formulate novel control techniques and improve on existing ones. This thesis experimentally demonstrates the effectiveness of novel composite pulse schemes for suppressing error in quantum bits. Furthermore, the thesis derives and demonstrates a novel predictive technique for stabilising oscillators by means of combining multiple frequency measurements against a quantum reference. The thesis therefore advances the theoretical understanding of a frequency-domain formalism for noise-affected quantum systems, on which basis it presents and demonstrates novel and improved techniques for mitigating the effects of such noise on the user's precision control over the system