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Title: Ontological models and reference frames in quantum mechanics
Author: Harrigan, Nicholas
ISNI:       0000 0001 3532 5567
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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On trying to describe quantum mechanics to a non-physicist, one often receives the response 'What does that really mean?' or alternatively 'What use is that?' Although these questions may seem naiVe, their answers are neither obvious nor even fully understood. In this thesis we present research aiming to help build answers to these questions. The first part of the thesis tries to shed some light on 'what quantum mechanics really means' by turning the question on its head and asking 'does quantum mechanics mean anything real?' The foundational issue of whether quantum mechanics is 'compatible with a realistic picture of our universe has puzzled some ofthe greatest physicists for over a hundred years. The approach we adopt is to begin by assuming a priori that objects in our universe can, at some level, be described by definite real states, and then ask what constraints experimental evidence (in agreement with quantum mechanics) will place on any such realistic theory. Regardless of the success of such a realistic description of our universe, our motivation for this 'reductio ad absurdum' approach is that it allows us to extract clues about how any successful description of our universe must fail to be realistic in a purely classical sense. The aim is that this will hint towards the key properties that must distinguishany successful description of our universe from our classical way of thinking. In order to quantitatively pursue this approach we build a generalized extension ofthe ontological model formalism, which allows one to compare and contrast a wide set ofrealistic theories within a single framework. We show how this formalism can clarify existing constraints placed on realism by quantum mechanics, such as non-locality, and then use it to derive a new requirement ofrealistic theories called deficiency. This is closely related to the property of contextuality, which was shown by Kochen and Specker to be necessary in any realistic interpretation of quantum mechanics. After having discussed the possibilities for what quantum behaviour could mean, the second part of this thesis considers how one might be able to make practical use ofthis behaviour, regardless ofhow one interprets it. The fields of quantum computation and quantum information offer very promising applications ofquantum mechanics. However, despite the promise it holds, the transmission and manipulation ofinformation solely with quantum systems still faces challenges which must be overcome before the technology can reach fruition. We consider the problem ofhow, within a completely quantum mechanical architecture, one might use quantum information to provide reference frames for information transfers. Specifically, we discuss how one might produce quantum mechanical reference frames necessary in crucial quantum information tasks such as violating Bell inequalities.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available