50 research outputs found
Modelización de un sistema territorial “urbano-rural” para la evaluación de su sostenibilidad. Aplicación a una zona representativa del País Vasco
El desarrollo de una base de conocimiento común y sólida que permita la máxima objetividad y transparencia en la evaluación de la sostenibilidad dentro del proceso de toma de decisiones, constituye uno de los pilares básicos para su implementación en el planeamiento estratégico y la gestión del territorio. La caracterización del sistema ecológico-ambiental, económico, social e
institucional que es objeto de gestión constituye un paso clave en el conocimiento de la red de relaciones que subyace al funcionamiento del sistema y de las interacciones responsables de potenciales sinergias. La traducción de esta información en modelos conceptuales y matemáticos
constituye una herramienta útil en el desarrollo de indicadores de sostenibilidad eficaces y relevantes, enfocados desde las necesidades de gestión. En este trabajo se presenta el modelo conceptual que define los componentes e interacciones de un sistema urbano-rural representativo del País Vasco, así como su marco de evaluación.One of the most important factors in introducing the concept of sustainability into strategic planning and territorial management is the development of a shared, solid knowledge base. This knowledge base should ensure maximum objectivity and transparency in sustainability assessment within the decision-making process. A description of the ecological-environmental, economic, social and institutional system that is to be managed is needed in order to develop knowledge about the network of relations that underlie the functioning of the system and the interactions that are responsible for potential synergies. The transformation of this information into conceptual and mathematical models is a useful tool for developing effective and relevant sustainability indicators that are oriented towards management needs. This paper presents a conceptual model that defines the components and interactions of a representative urban-rural system in the Basque Country. It also discusses the assessment frame for this model
Modelización de un sistema territorial "urbano-rural" para la evaluación de su sostenibilidad. Aplicación a una zona representativa del País Vasco
El desarrollo de una base de conocimiento común y sólida que permita la máxima objetividad y transparencia en la evaluación de la sostenibilidad dentro del proceso de toma de decisiones, constituye uno de los pilares básicos para su implementación en el planeamiento estratégico y la gestión del territorio. La caracterización del sistema ecológico-ambiental, económico, social e
institucional que es objeto de gestión constituye un paso clave en el conocimiento de la red de relaciones que subyace al funcionamiento del sistema y de las interacciones responsables de potenciales sinergias. La traducción de esta información en modelos conceptuales y matemáticos
constituye una herramienta útil en el desarrollo de indicadores de sostenibilidad eficaces y relevantes, enfocados desde las necesidades de gestión. En este trabajo se presenta el modelo conceptual que define los componentes e interacciones de un sistema urbano-rural representativo del País Vasco, así como su marco de evaluación.One of the most important factors in introducing the concept of sustainability into strategic planning and territorial management is the development of a shared, solid knowledge base. This knowledge base should ensure maximum objectivity and transparency in sustainability assessment within the decision-making process. A description of the ecological-environmental, economic, social and institutional system that is to be managed is needed in order to develop knowledge about the network of relations that underlie the functioning of the system and the interactions that are responsible for potential synergies. The transformation of this information into conceptual and mathematical models is a useful tool for developing effective and relevant sustainability indicators that are oriented towards management needs. This paper presents a conceptual model that defines the components and interactions of a representative urban-rural system in the Basque Country. It also discusses the assessment frame for this model
Adding control to arbitrary unknown quantum operations
While quantum computers promise significant advantages, the complexity of
quantum algorithms remains a major technological obstacle. We have developed
and demonstrated an architecture-independent technique that simplifies adding
control qubits to arbitrary quantum operations-a requirement in many quantum
algorithms, simulations and metrology. The technique is independent of how the
operation is done, does not require knowledge of what the operation is, and
largely separates the problems of how to implement a quantum operation in the
laboratory and how to add a control. We demonstrate an entanglement-based
version in a photonic system, realizing a range of different two-qubit gates
with high fidelity.Comment: 9 pages, 8 figure
Can One Trust Quantum Simulators?
Various fundamental phenomena of strongly-correlated quantum systems such as
high- superconductivity, the fractional quantum-Hall effect, and quark
confinement are still awaiting a universally accepted explanation. The main
obstacle is the computational complexity of solving even the most simplified
theoretical models that are designed to capture the relevant quantum
correlations of the many-body system of interest. In his seminal 1982 paper
[Int. J. Theor. Phys. 21, 467], Richard Feynman suggested that such models
might be solved by "simulation" with a new type of computer whose constituent
parts are effectively governed by a desired quantum many-body dynamics.
Measurements on this engineered machine, now known as a "quantum simulator,"
would reveal some unknown or difficult to compute properties of a model of
interest. We argue that a useful quantum simulator must satisfy four
conditions: relevance, controllability, reliability, and efficiency. We review
the current state of the art of digital and analog quantum simulators. Whereas
so far the majority of the focus, both theoretically and experimentally, has
been on controllability of relevant models, we emphasize here the need for a
careful analysis of reliability and efficiency in the presence of
imperfections. We discuss how disorder and noise can impact these conditions,
and illustrate our concerns with novel numerical simulations of a paradigmatic
example: a disordered quantum spin chain governed by the Ising model in a
transverse magnetic field. We find that disorder can decrease the reliability
of an analog quantum simulator of this model, although large errors in local
observables are introduced only for strong levels of disorder. We conclude that
the answer to the question "Can we trust quantum simulators?" is... to some
extent.Comment: 20 pages. Minor changes with respect to version 2 (some additional
explanations, added references...
Out-of-equilibrium physics in driven dissipative coupled resonator arrays
Coupled resonator arrays have been shown to exhibit interesting many- body
physics including Mott and Fractional Hall states of photons. One of the main
differences between these photonic quantum simulators and their cold atoms
coun- terparts is in the dissipative nature of their photonic excitations. The
natural equi- librium state is where there are no photons left in the cavity.
Pumping the system with external drives is therefore necessary to compensate
for the losses and realise non-trivial states. The external driving here can
easily be tuned to be incoherent, coherent or fully quantum, opening the road
for exploration of many body regimes beyond the reach of other approaches. In
this chapter, we review some of the physics arising in driven dissipative
coupled resonator arrays including photon fermionisa- tion, crystallisation, as
well as photonic quantum Hall physics out of equilibrium. We start by briefly
describing possible experimental candidates to realise coupled resonator arrays
along with the two theoretical models that capture their physics, the
Jaynes-Cummings-Hubbard and Bose-Hubbard Hamiltonians. A brief review of the
analytical and sophisticated numerical methods required to tackle these systems
is included.Comment: Chapter that appeared in "Quantum Simulations with Photons and
Polaritons: Merging Quantum Optics with Condensed Matter Physics" edited by
D.G.Angelakis, Quantum Science and Technology Series, Springer 201
Topological Photonics
Topology is revolutionizing photonics, bringing with it new theoretical
discoveries and a wealth of potential applications. This field was inspired by
the discovery of topological insulators, in which interfacial electrons
transport without dissipation even in the presence of impurities. Similarly,
new optical mirrors of different wave-vector space topologies have been
constructed to support new states of light propagating at their interfaces.
These novel waveguides allow light to flow around large imperfections without
back-reflection. The present review explains the underlying principles and
highlights the major findings in photonic crystals, coupled resonators,
metamaterials and quasicrystals.Comment: progress and review of an emerging field, 12 pages, 6 figures and 1
tabl
Quantum walks: a comprehensive review
Quantum walks, the quantum mechanical counterpart of classical random walks,
is an advanced tool for building quantum algorithms that has been recently
shown to constitute a universal model of quantum computation. Quantum walks is
now a solid field of research of quantum computation full of exciting open
problems for physicists, computer scientists, mathematicians and engineers.
In this paper we review theoretical advances on the foundations of both
discrete- and continuous-time quantum walks, together with the role that
randomness plays in quantum walks, the connections between the mathematical
models of coined discrete quantum walks and continuous quantum walks, the
quantumness of quantum walks, a summary of papers published on discrete quantum
walks and entanglement as well as a succinct review of experimental proposals
and realizations of discrete-time quantum walks. Furthermore, we have reviewed
several algorithms based on both discrete- and continuous-time quantum walks as
well as a most important result: the computational universality of both
continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing
Journa
Nano-Opto-Electro-Mechanical Systems
A new class of hybrid systems that couple optical, electrical and mechanical
degrees of freedom in nanoscale devices is under development in laboratories
worldwide. These nano-opto-electro-mechanical systems (NOEMS) offer
unprecedented opportunities to dynamically control the flow of light in
nanophotonic structures, at high speed and low power consumption. Drawing on
conceptual and technological advances from cavity optomechanics, they also bear
the potential for highly efficient, low-noise transducers between microwave and
optical signals, both in the classical and quantum domains. This Progress
Article discusses the fundamental physical limits of NOEMS, reviews the recent
progress in their implementation, and suggests potential avenues for further
developments in this field.Comment: 27 pages, 3 figures, 2 boxe
Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package
This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design
Diffusion Monte Carlo Study of Para -Diiodobenzene Polymorphism Revisited
We revisit our investigation of the diffusion Monte Carlo (DMC) simulation of p-DIB molecular crystal polymorphism. [J. Phys. Chem. Lett. 2010, 1, 1789-1794] We perform, for the first time, a rigorous study of finite-size effects and choice of nodal surface on the prediction of polymorph stability in molecular crystals using fixed-node DMC. Our calculations are the largest which are currently feasible using the resources of the K computer and provide insights into the formidable challenge of predicting such properties from first principles. In particular, we show that finite-size effects can influence the trial nodal surface of a small (1×1×1) simulation cell considerably. We therefore repeated our DMC simulations with a 1×3×3 simulation cell, which is the largest such calculation to date. We used a DFT nodal surface generated with the PBE functional and we accumulated statistical samples with ∼6.4×105 core-hours for each polymorph. Our final results predict a polymorph stability consistent with experiment, but indicate that results in our previous paper were somewhat fortuitous. We analyze the finite-size errors using model periodic Coulomb (MPC) interactions and kinetic energy corrections, according to the CCMH scheme of Chiesa, Ceperley, Martin, and Holzmann. We investigate the dependence of the finite-size errors on different aspect ratios of the simulation cell (k-mesh convergence) in order to understand how to choose an appropriate ratio for the DMC calculations. Even in the most expensive simulations currently possible, we show that the finite size errors in the DMC total energies are far larger than the energy difference between the two polymorphs, although error cancellation means that the polymorph prediction is accurate. Finally, we found that the T-move scheme is essential for these massive DMC simulations in order to circumvent population explosions and large time-step biases.Chemistry and Chemical Biolog