Universally optimal noisy quantum walks on complex networks

Caruso, Filippo

doi:10.1088/1367-2630/16/5/055015

Cited by 48 publications

(89 citation statements)

References 69 publications

(136 reference statements)

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“…A com- mon interpretation of ENAQT is that it regains (some of) the efficiency lost due to the energetic network disorder 5 . Clearly, here a combination of detuning and environmental coupling unlocks a maximal current which exceeds what is available from the archetypal idealised quantum channel 55 (i.e. a noiseless degenerate chain for end-to-end transport).…”

Section: Resultsmentioning

confidence: 99%

Environment-assisted quantum transport through single-molecule junctions

Sowa

Mol

Briggs

et al. 2017

Phys. Chem. Chem. Phys.

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Single-molecule electronics has been envisioned as the ultimate goal in the miniaturisation of electronic circuits. While the aim of incorporating single-molecule junctions into modern technology still proves elusive, recent developments in this field have begun to enable experimental investigation of fundamental concepts within the area of chemical physics. One such phenomenon is the concept of Environment-Assisted Quantum Transport which has emerged from the investigation of exciton transport in photosynthetic complexes. Here, we study charge transport through a two-site molecular junction coupled to a vibrational environment. We demonstrate that vibrational interactions can significantly enhance the current through specific molecular orbitals. Our study offers a clear pathway towards finding and identifying environment-assisted transport phenomena in charge transport settings.

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Section: Resultsmentioning

confidence: 99%

Environment-assisted quantum transport through single-molecule junctions

Sowa

Mol

Briggs

et al. 2017

Phys. Chem. Chem. Phys.

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“…Therefore, the possibility to experimentally reproduce NAT effects in purely optical networks with controllable parameters and topology, would allow one to verify the predictions of NAT models in simple test systems. Moreover, the investigation of the system response, when network parameters and noise characteristics are varied, would permit the optimization of specific networks towards maximum transport efficiency [19]. Recently, an optical platform consisting in a network of coupled cavities has been theoretically proposed as simulator of the basic mechanisms underlying NAT [20].…”

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confidence: 99%

Observation of Noise-Assisted Transport in an All-Optical Cavity-Based Network

Viciani¹,

Lima²,

Bellini³

et al. 2015

Phys. Rev. Lett.

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Recent theoretical and experimental efforts have shown the remarkable and counter-intuitive role of noise in enhancing the transport efficiency of complex systems. Here, we realize simple, scalable, and controllable optical fiber cavity networks that allow us to analyze the performance of transport networks for different conditions of interference, dephasing and disorder. In particular, we experimentally demonstrate that the transport efficiency reaches a maximum when varying the external dephasing noise, i.e. a bell-like shape behavior that had been predicted only theoretically. These optical platforms are very promising simulators of quantum transport phenomena, and could be used, in particular, to design and test optimal topologies of artificial light-harvesting structures for future solar energy technologies. The transmission of energy through interacting systems plays a crucial role in many fields of physics, chemistry, and biology. In particular, the study and a full understanding of the mechanisms driving the energy transport may open interesting perspectives both to improve the process of transferring quantum or classical information across complex networks, and to explain the high efficiency of the excitation transfer through a network of chromophores in photosynthetic systems. Indeed, recently, several experiments on light-harvesting complexes have suggested a possible correlation between the remarkable transport efficiency of these systems and the presence of long-lived quantum effects, observed also at room temperature [1][2][3][4][5][6].Stimulated by these results, a large theoretical effort has been undertaken to study transport mechanisms through a network of chromophores or, more in general, through a complex network, bringing to evidence the active role of noise in energy transport. In fact, it is usually accepted that the uncontrollable interaction of a transmission network with an external noisy environment negatively affects the transport efficiency by reducing the coherence of the system [7]. However, the noise has also been found to play a positive role in assisting the transport of energy [8][9][10][11][12][13] and information [14], and loss-induced optical transparency has been observed in waveguide systems [15]. In certain circumstances, the presence of noise can lead to the inhibition of destructive interference and to the opening of additional pathways for excitation transfer, with a consequent increase of the transport efficiency [10]. This phenomenon has generally gone under the name of noise-assisted transport (NAT). In this context, the role of geometry has been theoretically analyzed in terms of structure optimization [16], in the case of disordered systems [17], and also for the proposal of design principles for biomimetic structures [18]. Therefore, the possibility to experimentally reproduce NAT effects in purely optical networks with controllable parameters and topology, would allow one to verify the predictions of NAT models in simple test systems. Moreover, the investigation...

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“…A possible drawback of these approaches, as we explain below, is the potential physical implausibility of the perturbed models, especially when the transformations involve 'deleting' coupling terms or making uncorrelated perturbations to the Hamiltonian arXiv:1704.01795v2 [physics.chem-ph] 22 May 2017 2 matrix. Other strategies deploy abstract models of the transport system [13,19,[21][22][23]] to learn general principles from idealised 'network' models that may operate to a greater or lesser extent in realistic systems.In this Letter, we incorporate the best of the above strategies to address two key questions on the structuredynamics relationship for exciton transport: (i) which structural motifs influence exciton dynamics in typical physically-plausible multi-chromophore complexes? and (ii) do naturally occurring complexes appear to be attuned for certain transport tasks (by exploiting these motifs or otherwise)?…”

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confidence: 99%

Structure-Dynamics Relation in Physically-Plausible Multi-Chromophore Systems

Knee¹,

Rowe

Smith³

et al. 2017

J. Phys. Chem. Lett.

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We study a large number of physically-plausible arrangements of chromophores, generated via a computational method involving stochastic real-space transformations of a naturally occurring 'reference' structure, illustrating our methodology using the well-studied Fenna-Matthews-Olson complex (FMO). To explore the idea that the natural structure has been tuned for efficient energy transport we use an atomic transition charge method to calculate the excitonic couplings of each generated structure and a Lindblad master equation to study the quantum transport of an exciton from a 'source' to a 'drain' chromophore. We find significant correlations between structure and transport efficiency: High-performing structures tend to be more compact and, among those, the best structures display a certain orientation of the chromophores, particularly the chromophore closest to the source-to-drain vector. We conclude that, subject to reasonable, physically-motivated constraints, the FMO complex is highly attuned to the purpose of energy transport, partly by exploiting these structural motifs.The process of excitonic energy transport is of great interest across many fields of study, from evolutionary biology to the engineering of solar cells. It is a key component of both natural photosynthesis (occurring in light harvesting complexes (LHCs), which are assemblages of chromophores found in a famously 'warm and wet' environment) and artificial photovoltaics. It is tempting to suggest that, since natural selection has had perhaps billions of years [1] over which to improve the efficiency of the process, we might learn from nature how to better engineer artificial light harvesting systems. This view has gathered interest in recent years, in tandem with claims that naturally occurring systems can exhibit outstandingly high efficiency [2, 3]. It is often said that quantum coherence could play a pivotal role in enhancing transport [4][5][6][7] through constructive interference of excitation pathways (although this is hotly debated [8][9][10]) and that the structural arrangement of chromophores has been optimised for this functionality [3]. Contrariwise, it might be suggested that efficient transport through a network of chromophores is actually generic and most of the possible structural arrangements would show similar performance. It is difficult to draw conclusions about the general structure-dynamics relationship from studying only a handful of naturally occurring LHCs. Indeed, while it is clearly desirable to learn from the results of natural selection [11], we must also be able to relax the constraints that it operated under in order to uncover the potential for technological advantage, while at all times keeping our imagination on a short enough leash so that any new structures remain physically plausible. * gk@physics.org † animesh.datta@warwick.ac.ukTheoretical efforts have so far proceeded along two paths. The first technique is to randomly 'sprinkle' pointlike electrical dipoles into a restricted volume: This approach has all...

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Universally optimal noisy quantum walks on complex networks

Cited by 48 publications

References 69 publications

Environment-assisted quantum transport through single-molecule junctions

Environment-assisted quantum transport through single-molecule junctions

Observation of Noise-Assisted Transport in an All-Optical Cavity-Based Network

Structure-Dynamics Relation in Physically-Plausible Multi-Chromophore Systems

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