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dc.contributor.advisorLovett, Brendon W.
dc.contributor.authorStrathearn, Aidan
dc.coverage.spatial[5], 106 p.en_US
dc.date.accessioned2021-09-23T12:25:35Z
dc.date.available2021-09-23T12:25:35Z
dc.date.issued2020-07
dc.identifier.urihttp://hdl.handle.net/10023/24008
dc.description.abstractAccurately modelling the behaviour of quantum systems interacting with the environment is vital to the development of quantum technology. Open quantum systems are well understood when the influence of their environment is weak, but the problem of modelling general systems away from this limit remains difficult. Currently, all approaches to making this problem tractable require some assumption about the nature of the system and its environment. In this thesis a general and efficient numerical method for calculating observables of open quantum systems is presented. The method is to express the exact equations of motion that describe the evolution of a general open quantum system as a tensor network, whose structure allows for a decomposition in terms of matrix products that can be efficiently compressed in size. The power and versatility of the method is demonstrated by using it to study three contrasting models. The first of these is the Ohmic Spin-Boson model, in which the location of the localisation phase transition is identified by analysing the dissipative spin dynamics. This requires high precision numerical calculations, which are shown to be carried out with high efficiency. The second model is that of two spatially separated spins interacting with the same environment, for which no other exact results are available. Here the environment is seen to mediate interaction between the spins, which is intuitively found to be longer ranged for a lower spatial dimension. Finally, an experimentally relevant model of a driven quantum dot is considered. Calculations of the emission spectrum of the dot reveal complex interplay between the coherent driving and the dissipative influence of phonons. In particular the phonon sideband in the spectrum is found to be supressed as the driving of the dot is strengthened.en_US
dc.description.sponsorship"This work was supported by the Engineering and Physical Sciences Research Council [EPL/505079/1]. This work was supported by the University of St Andrews (Department of Physics and Astronomy). " -- Fundingen
dc.language.isoenen_US
dc.publisherUniversity of St Andrews
dc.relationModelling non-Markovian quantum systems using tensor networks (thesis data). Strathearn, A. DOI: https://doi.org/10.5281/zenodo.1322407en
dc.relation.urihttps://doi.org/10.5281/zenodo.1322407
dc.subject.lccQC174.45S88
dc.subject.lcshQuantum systemsen
dc.subject.lcshQuantum theoryen
dc.subject.lcshQuantum dotsen
dc.titleModelling non-Markovian quantum systems using tensor networksen_US
dc.typeThesisen_US
dc.contributor.sponsorEngineering and Physical Sciences Research Council (EPSRC)en_US
dc.contributor.sponsorUniversity of St Andrews. School of Physics & Astronomyen_US
dc.type.qualificationlevelDoctoralen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US
dc.rights.embargodate2022-03-05
dc.rights.embargoreasonThesis restricted in accordance with University regulations. Print and electronic copy restricted until 5th March 2022en
dc.identifier.grantnumberEPL/505079/1en_US


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