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The role of quantum coherence in dimer and trimer excitation energy transfer
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. (Quantum information theory)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. (Quantum information theory)
2017 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, article id 113015Article in journal (Refereed) Published
Abstract [en]

Recent progress in resource theory of quantum coherence has resulted in measures to quantify coherence in quantum systems. Especially, the l1-norm and relative entropy of coherence have been shown to be proper quantifiers of coherence and have been used to investigate coherence properties in different operational tasks. Since long-lasting quantum coherence has been experimentally confirmed in a number of photosynthetic complexes, it has been debated if and how coherence is connected to the known efficiency of population transfer in such systems. In this study, we investigate quantitatively the relationship between coherence, as quantified by l1 norm and relative entropy of coherence, and efficiency, as quantified by fidelity, for population transfer between end-sites in a network of two-level quantum systems. In particular, we use the coherence averaged over the duration of the population transfer in order to carry out a quantitative comparision between coherence and fidelity. Our results show that although coherence is a necessary requirement for population transfer, there is no unique relation between coherence and the efficiency of the transfer process.

Place, publisher, year, edition, pages
2017. Vol. 19, article id 113015
Keyword [en]
Quantum coherence, energy transport
National Category
Other Physics Topics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-327295DOI: 10.1088/1367-2630/aa916bISI: 000415196900003OAI: oai:DiVA.org:uu-327295DiVA: diva2:1130221
Funder
Swedish Research Council, D0413201Swedish National Infrastructure for Computing (SNIC), snic2017-7-17
Available from: 2017-08-08 Created: 2017-08-08 Last updated: 2018-02-21Bibliographically approved
In thesis
1. Quantum Resources for Efficient Excitation Energy Transfer in Natural and Artificial Pigment-Protein Molecular Aggregates
Open this publication in new window or tab >>Quantum Resources for Efficient Excitation Energy Transfer in Natural and Artificial Pigment-Protein Molecular Aggregates
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recently, long-lasting quantum effects in a number of photosynthetic complexes, which are pigment-protein molecular aggregates (PPMAs), were experimentally verified. These findings created an interest in trying to connect the known highly efficient excitation energy transfer (EET) in these systems to the existence of quantum effects such as quantum coherence and quantum correlations. It also raised the question of how these sensitive quantum effects can survive in such a macroscopic system.

This thesis explores the existence and possible role of quantum effects in the EET in PPMAs. These systems can be modeled as non-Markovian open quantum systems and quantum effects can be investigated and quantified by methods developed in quantum information theory.

Firstly, it is found that quantum nonlocal correlations in the EET in the Fenna-Matthews-Olson complex - a PPMA found in nature - are unlikely to exist when the initial excitation occurs in a natural manner. When the initial excitation occurs in an artificial manner by localization of the excitation on one pigment, nonlocal correlations exist on a short time scale. It is further found that in order for nonlocal correlations to be preserved in such a system, the excitation must be trapped on two pigments at the time and these pigments must not interact strongly with other pigments in the complex.

Secondly, it is shown that quantum coherence is not in general a resource for efficient EET in model systems consisting of a network of pigments; systems optimized with respect to the amount of coherence do not coincide with systems with optimal EET efficiency between two end-site pigments.

Thirdly, it is found that environmental effects and system-environment interactions can be tuned to optimize the EET efficiency in model PPMAs. The features of optimal environments highly depends on the structure of the pigment system and in particular, the relationship between the pigments excitation energies. It is further shown that a non-Markovian dynamics cannot be connected to an increased EET efficiency in these systems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 120
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1622
Keyword
Quantum coherence, quantum correlations, quantum nonlocality, open quantum systems, non-Markovian dynamics
National Category
Natural Sciences
Research subject
Chemistry with specialization in Quantum Chemistry
Identifiers
urn:nbn:se:uu:diva-339469 (URN)978-91-513-0211-9 (ISBN)
Public defence
2018-03-09, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-02-16 Created: 2018-01-19 Last updated: 2018-02-16

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