582 research outputs found
Dephasing-assisted transport: quantum networks and biomolecules
Original article can be found at: http://www.iop.org/EJ/journal/1367-2630/1 DOI: 10.1088/1367-2630/10/11/113019Transport phenomena are fundamental in physics. They allow for information and energy to be exchanged between individual constituents of communication systems, networks or even biological entities. Environmental noise will generally hinder the efficiency of the transport process. However, and contrary to intuition, there are situations in classical systems where thermal fluctuations are actually instrumental in assisting transport phenomena. Here we show that, even at zero temperature, transport of excitations across dissipative quantum networks can be enhanced by local dephasing noise. We explain the underlying physical mechanisms behind this phenomenon and propose possible experimental demonstrations in quantum optics. Our results suggest that the presence of entanglement does not play an essential role for energy transport and may even hinder it. We argue that Nature may be routinely exploiting dephasing noise and show that the transport of excitations in simplified models of light harvesting molecules does benefit from such noise assisted processes. These results point toward the possibility for designing optimized structures for transport, for example in artificial nanostructures, assisted by noise.Peer reviewe
Quantum dynamics of bio-molecular systems in noisy environments
We discuss three different aspects of the quantum dynamics of bio-molecular
systems and more generally complex networks in the presence of strongly coupled
environments. Firstly, we make a case for the systematic study of fundamental
structural elements underlying the quantum dynamics of these systems, identify
such elements and explore the resulting interplay of quantum dynamics and
environmental decoherence. Secondly, we critically examine some existing
approaches to the numerical description of system-environment interaction in
the non-perturbative regime and present a promising new method that can
overcome some limitations of existing methods. Thirdly, we present an approach
towards deciding and quantifying the non-classicality of the action of the
environment and the observed system-dynamics. We stress the relevance of these
tools for strengthening the interplay between theoretical and experimental
research in this field.Comment: Proceedings of the 22nd Solvay Conference in Chemistry on "Quantum
Effects in Chemistry and Biology
Open Quantum Systems. An Introduction
We revise fundamental concepts in the dynamics of open quantum systems in the
light of modern developments in the field. Our aim is to present a unified
approach to the quantum evolution of open systems that incorporates the
concepts and methods traditionally employed by different communities. We
present in some detail the mathematical structure and the general properties of
the dynamical maps underlying open system dynamics. We also discuss the
microscopic derivation of dynamical equations, including both Markovian and
non-Markovian evolutions.Comment: 100 pages, 3 figures. Updated version with typos corrected. Preprint
version of the published boo
Robust creation of entanglement between ions in spatially separate cavities
We present a protocol that allows the generation of a maximally entangled state between individual atoms held in spatially separate cavities. Assuming perfect detectors and neglecting spontaneous emission from the atoms, the resulting idealized scheme is deterministic. Under more realistic conditions, when the atom-cavity interaction departs from the strong coupling regime, and considering imperfect detectors, we show that the scheme is robust against experimental inefficiencies and yields probabilistic entanglement of very high fidelity
Quantum Non-Markovianity: Characterization, Quantification and Detection
We present a comprehensive and up to date review on the concept of quantum
non-Markovianity, a central theme in the theory of open quantum systems. We
introduce the concept of quantum Markovian process as a generalization of the
classical definition of Markovianity via the so-called divisibility property
and relate this notion to the intuitive idea that links non-Markovianity with
the persistence of memory effects. A detailed comparison with other definitions
presented in the literature is provided. We then discuss several existing
proposals to quantify the degree of non-Markovianity of quantum dynamics and to
witness non-Markovian behavior, the latter providing sufficient conditions to
detect deviations from strict Markovianity. Finally, we conclude by enumerating
some timely open problems in the field and provide an outlook on possible
research directions.Comment: Review article. Close to published versio
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