Diamond thin films:synthesis,caharacterisation and application in quantum information processing

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dc.contributor.authorMazhandu, Farai
dc.date.accessioned2020-01-27T09:40:18Z
dc.date.available2020-01-27T09:40:18Z
dc.date.issued2019
dc.descriptionA dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, May,2019en_ZA
dc.description.abstractA new era of quantum based technologies is currently unfolding and the most challenging amongst these is the quantum computer. A scalable and universal quantum computer stands on fast, reproducible and controllable high-coherence quantum bits (qubits). Quantum physics aspects such as superposition and entanglement are harnessed to provide the much needed improvement in capabilities to do information processing and simulation. Our work focuses on quantum technology based on quantum matter in diamond and the applications of quantum computers in the simulation of condensed matter physics phenomena. Superconducting qubits and spin qubits have different merits which can be combined to build a hybrid quantum processor. A four junction flux qubit is proposed for computation because of its fast and coherent control. Nitrogen doping of diamond gives rise to nitrogen-vacancy centers (NV), an aspect which is manipulate in this work as a quantum bus and register. The IBM Q cloud quantum computer is used to simulate effective coupling in a hybrid quantum system consisting of two spin qubits and a superconducting flux qubit. The NV- center in a diamond crystal is effectively coupled to a flux qubit through an external magnetic flux. This work shows that the coupling strengths between a flux qubit, electron spin, and nuclear spin evolve from weak to strong. Coupling between spin and superconducting flux qubit is a subject of ongoing research while direct coupling is the preferred mechanism. Effective coupling is achieved through tuning the excitation frequencies of the individual spins via external magnetic fields. A qubit is as good as the material it is built upon. Crucial to the successful operation of superconducting qubits is also the aspect of tunability and here we investigate quantum phase transitions in heavily boron doped diamond (HBDD) thin films using a cryogenic high field measurement system (CFMS). Our results confirm tunable behavior in HBDD thin films as shown by switching from superconducting to insulating regime below the critical temperatures. We were also able to show digital quantum implementation of entanglement, decoherence, and fidelity which are critical properties when it comes to building a scalable universal quantum computer. This work clearly demonstrates the importance of a quantum simulator to researchers. We are able to observe and study profound physical phenomena as well as test ideas towards development of a hybrid quantum computer based on boron doped nanodiamond.en_ZA
dc.description.librarianE.K. 2020en_ZA
dc.identifier.urihttps://hdl.handle.net/10539/28757
dc.language.isoenen_ZA
dc.titleDiamond thin films:synthesis,caharacterisation and application in quantum information processingen_ZA
dc.typeThesisen_ZA
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