2,031 research outputs found
Hamiltonian tomography of dissipative systems under limited access: A biomimetic case study
The identification of parameters in the Hamiltonian that describes complex
many-body quantum systems is generally a very hard task. Recent attention has
focused on such problems of Hamiltonian tomography for networks constructed
with two-level systems. For open quantum systems, the fact that injected
signals are likely to decay before they accumulate sufficient information for
parameter estimation poses additional challenges. In this paper, we consider
use of the gateway approach to Hamiltonian tomography
\cite{Burgarth2009,Burgarth2009a} to complex quantum systems with a limited set
of state preparation and measurement probes. We classify graph properties of
networks for which the Hamiltonian may be estimated under equivalent conditions
on state preparation and measurement. We then examine the extent to which the
gateway approach may be applied to estimation of Hamiltonian parameters for
network graphs with non-trivial topologies mimicking biomolecular systems.Comment: 6 page
Low Beta MHD Equilibrium Including a Static Magnetic Island in a Straight Heliotron Configuraion Obtained with a Parallel Diffusion Equation
Numerical Calculation of MHD Equilibria Including Static Magnetic Islands in a Straight Heliotron Configuration by Means of a Field Line Tracing Method
Effects of Static Magnetic Island on Resistive Interchange Mode in a Straight Heliotron Plasma
Effect of Parallel Diffusion of Equilibrium Pressure on Interaction between Interchange Mode and Static Magnetic Island
Quantum entanglement phenomena in photosynthetic light harvesting complexes
AbstractWe review recent theoretical calculations of quantum entanglement in photosynthetic light harvesting complexes. These works establish, for the first time, a manifestation of this characteristically quantum mechanical phenomenon in biologically functional structures. We begin by summarizing calculations on model biomolecular systems that aim to reveal non-trivial characteristics of quantum entanglement in non-equilibrium biological environments. We then discuss and compare several calculations performed recently of excitonic dynamics in the Fenna-Matthews-Olson light harvesting complex and of the electronic entanglement present in this widely studied pigment-protein structure. We point out the commonalities between the derived results and also identify and explain the differences. We also discuss recent work that examines entanglement in the structurally more intricate light harvesting complex II (LHCII). During this overview, we take the opportunity to clarify several subtle issues relating to entanglement in such biomolecular systems, including the role of entanglement in biological function, the complexity of dynamical modeling that is required to capture the salient features of entanglement in such biomolecular systems, and the relationship between entanglement and other quantum mechanical features that are observed and predicted in light harvesting complexes. Finally, we suggest possible extensions of the current work and also review the options for experimental confirmation of the predicted entanglement phenomena in light harvesting complexes
Spatial propagation of excitonic coherence enables ratcheted energy transfer
Experimental evidence shows that a variety of photosynthetic systems can
preserve quantum beats in the process of electronic energy transfer, even at
room temperature. However, whether this quantum coherence arises in vivo and
whether it has any biological function have remained unclear. Here we present a
theoretical model that suggests that the creation and recreation of coherence
under natural conditions is ubiquitous. Our model allows us to theoretically
demonstrate a mechanism for a ratchet effect enabled by quantum coherence, in a
design inspired by an energy transfer pathway in the Fenna-Matthews-Olson
complex of the green sulfur bacteria. This suggests a possible biological role
for coherent oscillations in spatially directing energy transfer. Our results
emphasize the importance of analyzing long-range energy transfer in terms of
transfer between inter-complex coupling (ICC) states rather than between site
or exciton states.Comment: Accepted version for Phys. Rev. E. 14 pages, 7 figure
Application of indirect Hamiltonian tomography to complex systems with short decoherence times
Quantum entanglement in photosynthetic light harvesting complexes
Light harvesting components of photosynthetic organisms are complex, coupled,
many-body quantum systems, in which electronic coherence has recently been
shown to survive for relatively long time scales despite the decohering effects
of their environments. Within this context, we analyze entanglement in
multi-chromophoric light harvesting complexes, and establish methods for
quantification of entanglement by presenting necessary and sufficient
conditions for entanglement and by deriving a measure of global entanglement.
These methods are then applied to the Fenna-Matthews-Olson (FMO) protein to
extract the initial state and temperature dependencies of entanglement. We show
that while FMO in natural conditions largely contains bipartite entanglement
between dimerized chromophores, a small amount of long-range and multipartite
entanglement exists even at physiological temperatures. This constitutes the
first rigorous quantification of entanglement in a biological system. Finally,
we discuss the practical utilization of entanglement in densely packed
molecular aggregates such as light harvesting complexes.Comment: 14 pages, 7 figures. Improved presentation, published versio
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