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Title: Decoherence and measurement in solid state quantum computers
Author: Barrett, S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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The discovery of quantum algorithms that can outperform the best known classical algorithms for certain problems has, in recent years, instigated a rapid growth in the study of quantum computation. A number of schemes for the practical implementation of quantum logic in a semiconductor device have been proposed. These schemes, being an extension of existing semiconductor technology, have the potential to be scaled to a large number of qubits. There is now a substantial experimental effort, worldwide, to build quantum logid devices in semiconductor systems. However, a number of important issues must be tackled if such a device is to be realized. In this work, I concentrate on theoretical aspects of two central problems in the implementation of a solid state quantum computer: decoherence and readout. After introducing some concepts in quantum information and quantum computation, I review a number of recent proposals for semiconductor based quantum logic: I then consider the problem of decoherence of a single charge qubit and propose an experimentally viable scheme to measure the decoherence rate! Subsequently, I consider a potentially serious decoherence mechanism in an electron spin based quantum computer. I show that the coupling of the charge degrees of freedom of the electrons to environmental electromagnetic fluctuations can lead to errors in the operation of a quantum logic gate. Finally, I consider the problem of quantum measurement (readout) of the spin state of electrons in a semiconductor based quantum computer I describe a method whereby the spin degree of freedom of a pair of electrons in a two-site system can be measured by observing spin-dependent charge fluctuations with a nearby electrometer. I argue that the measurement could be performed with existing detector technology.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available