Metrology, metastability and dynamical phase transitions in open quantum systems

In this thesis we explore aspects of dynamics of open quantum systems related to coherence and quantum correlations - necessary resources for enhanced quantum metrology and quantum computation. We first discuss limits to the precision of parameter estimation when using a quantum system in the pres...

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Main Author:	Macieszczak, Katarzyna
Format:	Thesis (University of Nottingham only)
Language:	English
Published:	2017
Online Access:	http://eprints.nottingham.ac.uk/39811/ http://eprints.nottingham.ac.uk/39811/1/KMacieszczakThesis.pdf

id	nottingham-39811
recordtype	eprints
spelling	nottingham-398112017-10-13T17:01:30Z http://eprints.nottingham.ac.uk/39811/ Metrology, metastability and dynamical phase transitions in open quantum systems Macieszczak, Katarzyna In this thesis we explore aspects of dynamics of open quantum systems related to coherence and quantum correlations - necessary resources for enhanced quantum metrology and quantum computation. We first discuss limits to the precision of parameter estimation when using a quantum system in the presence of noise. To this end we introduce a variational principle for the quantum Fisher information (QFI) bounding the estimation errors of any measurement, which motivates an efficient iterative algorithm for finding optimal system preparations for noisy estimation experiments. Furthermore, we investigate influence of noise correlations on the precision in phase and frequency estimation, by delivering bounds for both spatially and temporarily correlated (non-Markovian) dephasing noise. This allows us to prove the Zeno limit in frequency estimation, conjectured in Phys. Rev. A 84, 012103 (2011) and Phys. Rev. Lett. 109, 233601 (2012). The enhanced estimation precision in quantum metrology can be, however, achieved only using highly entangled states. We propose a scheme of generating such highly correlated states as outputs of Markovian open quantum systems near first-order dynamical phase transitions. We show that the quadratic scaling of the QFI with time is present for experiments within the correlation time of the dynamics and describe a theoretical scheme for quantum enhanced estimation of an optical phase-shift using the photons being emitted from an intermittent quantum system. Finally, we establish the basis for a theory of metastability in Markovian open quantum systems, by extending methods from classical stochastic dynamics. We argue that the partial relaxation into long-lived metastable states - distinct from the asymptotic stationary state - may preserve initial coherences within decoherence-free subspaces or noiseless subsystems, thus allowing for quantum computation during the metastable regime. 2017-07-12 Thesis (University of Nottingham only) NonPeerReviewed application/pdf en cc_by_nc_nd http://eprints.nottingham.ac.uk/39811/1/KMacieszczakThesis.pdf Macieszczak, Katarzyna (2017) Metrology, metastability and dynamical phase transitions in open quantum systems. PhD thesis, University of Nottingham.
repository_type	Digital Repository
institution_category	Local University
institution	University of Nottingham Malaysia Campus
building	Nottingham Research Data Repository
collection	Online Access
language	English
description	In this thesis we explore aspects of dynamics of open quantum systems related to coherence and quantum correlations - necessary resources for enhanced quantum metrology and quantum computation. We first discuss limits to the precision of parameter estimation when using a quantum system in the presence of noise. To this end we introduce a variational principle for the quantum Fisher information (QFI) bounding the estimation errors of any measurement, which motivates an efficient iterative algorithm for finding optimal system preparations for noisy estimation experiments. Furthermore, we investigate influence of noise correlations on the precision in phase and frequency estimation, by delivering bounds for both spatially and temporarily correlated (non-Markovian) dephasing noise. This allows us to prove the Zeno limit in frequency estimation, conjectured in Phys. Rev. A 84, 012103 (2011) and Phys. Rev. Lett. 109, 233601 (2012). The enhanced estimation precision in quantum metrology can be, however, achieved only using highly entangled states. We propose a scheme of generating such highly correlated states as outputs of Markovian open quantum systems near first-order dynamical phase transitions. We show that the quadratic scaling of the QFI with time is present for experiments within the correlation time of the dynamics and describe a theoretical scheme for quantum enhanced estimation of an optical phase-shift using the photons being emitted from an intermittent quantum system. Finally, we establish the basis for a theory of metastability in Markovian open quantum systems, by extending methods from classical stochastic dynamics. We argue that the partial relaxation into long-lived metastable states - distinct from the asymptotic stationary state - may preserve initial coherences within decoherence-free subspaces or noiseless subsystems, thus allowing for quantum computation during the metastable regime.
format	Thesis (University of Nottingham only)
author	Macieszczak, Katarzyna
spellingShingle	Macieszczak, Katarzyna Metrology, metastability and dynamical phase transitions in open quantum systems
author_facet	Macieszczak, Katarzyna
author_sort	Macieszczak, Katarzyna
title	Metrology, metastability and dynamical phase transitions in open quantum systems
title_short	Metrology, metastability and dynamical phase transitions in open quantum systems
title_full	Metrology, metastability and dynamical phase transitions in open quantum systems
title_fullStr	Metrology, metastability and dynamical phase transitions in open quantum systems
title_full_unstemmed	Metrology, metastability and dynamical phase transitions in open quantum systems
title_sort	metrology, metastability and dynamical phase transitions in open quantum systems
publishDate	2017
url	http://eprints.nottingham.ac.uk/39811/ http://eprints.nottingham.ac.uk/39811/1/KMacieszczakThesis.pdf
first_indexed	2018-09-06T13:01:58Z
last_indexed	2018-09-06T13:01:58Z
_version_	1610863259937669120

Metrology, metastability and dynamical phase transitions in open quantum systems

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