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Optimisation and attainability of magnetometry with qubit probes
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Friel, James F. (2022) Optimisation and attainability of magnetometry with qubit probes. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3941352
Abstract
Quantum enhanced metrology potentially offers a great advantage to the estimation of magnetic fields. One of the greatest hurdles to overcome in unlocking this advantage is overcoming the detrimental effects of noise. The forms the main motivation of this thesis. What are the optimal states for quantum enhanced estimation of magnetic fields? A natural secondary motivation that follows from thinking practically about the impacts of noise is, how do we generate these states?
One of the subtleties involved in the analysis of using quantum systems for magnetic field estimation is the different figures of merit available and how informative each may be. To begin we show that the intuitively optimal 3D-Greenberger–Horne–Zeilinger state is indeed optimal for large numbers of qubits. We develop a novel genetic inspired algorithm to find optimal states for low numbers of qubits.
Following this, we are dedicated to the study of the Holevo Cramer-Rao bound. This being the ultimate bound to a multiparameter quantum estimation problem. We compute the first analytic three parameter example of the Holevo Cramer-Rao bound and demonstrate that is it attainable with a projective measurement.
Moving beyond the case that can be analytically solved, we study the quantum limits of magnetometry in the presence of noise. Once we have examined the attainability of magnetometry with increasing copies of the input state, we develop another genetic inspired algorithm for the optimisation of quantum circuits to attain these limits.
To conclude, we present some preliminary investigations into using spin chains with local control and measurement on only one extremal edge for the estimation of a magnetic field with a simplified control set-up. In particular we look to utilise a sub-universal model that is simulable with linear space in the number of qubits.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics | ||||
Library of Congress Subject Headings (LCSH): | Magnetic fields -- Measurement, Quantum theory, Quantum systems, Metrology, Quantum measure theory, Noise -- Measurement, Interferometry | ||||
Official Date: | January 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Datta, Animesh | ||||
Format of File: | |||||
Extent: | xvii, 159 pages : illustrations | ||||
Language: | eng |
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