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Search Results: 1 - 10 of 144444 matches for " F. Galve "
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Array of planar Penning traps as a nuclear magnetic resonance molecule for quantum computation
G. Ciaramicoli,F. Galve,I. Marzoli,P. Tombesi
Physics , 2005, DOI: 10.1103/PhysRevA.72.042323
Abstract: An array of planar Penning traps, holding single electrons, can realize an artificial molecule suitable for NMR-like quantum information processing. The effective spin-spin coupling is accomplished by applying a magnetic field gradient, combined to the Coulomb interaction acting between the charged particles. The system lends itself to scalability, since the same substrate can easily accommodate an arbitrary number of traps. Moreover, the coupling strength is tunable and under experimental control. Our theoretical predictions take into account a realistic setting, within the reach of current technology.
Creation and manipulation of entanglement in spin chains far from equilibrium
F. Galve,D. Zueco,G. M. Reuther,S. Kohler,P. H?nggi
Physics , 2010, DOI: 10.1140/epjst/e2010-01220-5
Abstract: We investigate creation, manipulation, and steering of entanglement in spin chains from the viewpoint of quantum communication between distant parties. We demonstrate how global parametric driving of the spin-spin coupling and/or local time-dependent Zeeman fields produce a large amount of entanglement between the first and the last spin of the chain. This occurs whenever the driving frequency meets a resonance condition, identified as "entanglement resonance". Our approach marks a promising step towards an efficient quantum state transfer or teleportation in solid state system. Following the reasoning of Zueco et al. [1], we propose generation and routing of multipartite entangled states by use of symmetric tree-like structures of spin chains. Furthermore, we study the effect of decoherence on the resulting spin entanglement between the corresponding terminal spins.
Irreversible work and inner friction in quantum thermodynamic processes
F. Plastina,A. Alecce,T. J. G. Apollaro,G. Falcone,G. Francica,F. Galve,N. Lo Gullo,R. Zambrini
Physics , 2014, DOI: 10.1103/PhysRevLett.113.260601
Abstract: We discuss the thermodynamics of closed quantum systems driven out of equilibrium by a change in a control parameter and undergoing a unitary process. We compare the work actually done on the system with the one that would be performed along ideal adiabatic and isothermal transformations. The comparison with the latter leads to the introduction of irreversible work, while that with the former leads to the introduction of inner friction. We show that these two quantities can be treated on equal footing, as both can be linked with the heat exchanged in thermalization processes and both can be expressed as relative entropies. Furthermore, we show that a specific fluctuation relation for the entropy production associated with the inner friction exists, which allows the inner friction to be written in terms of its cumulants.
Nonequilibrium thermodynamics of a squeezed harmonic oscillator
Fernando Galve,Eric Lutz
Physics , 2008,
Abstract: We consider the thermodynamic properties of the squeezed vacuum state of a frequency--modulated quantum harmonic oscillator. We analytically relate the squeezing parameter to the irreversible work and the degree of nonadiabaticity of the frequency transformation. We furthermore determine the optimal modulation that leads to maximal squeezing, and discuss its implementation as well as the detection of squeezing in single cold ion traps.
Optimal nonequilibrium entanglement of nanomechanical oscillators
Fernando Galve,Eric Lutz
Physics , 2008, DOI: 10.1103/PhysRevA.79.032327
Abstract: We investigate nonequilibrium entanglement generation in a chain of harmonic oscillators with time-dependent linear coupling. We use optimal control theory to determine the coupling modulation that leads to maximum logarithmic negativity for a pair of opposite oscillators and show that it corresponds to a synchronization of the eigenmodes of the chain. We further analytically relate the maximum attainable entanglement to the irreversible work done to produce it, thus bridging nonequilibrium entanglement production and nonequilibrium thermodynamics.
On some impossible disentanglement puzzles
Fernando Galve Mauricio
Mathematics , 2012,
Abstract: In this article we prove the impossibility of some disentanglement puzzles, first building mathematical models that reflect the essential characteristics of these puzzles.
Revista de Estudios Cooperativos , 2010,
Abstract: El objetivo de este trabajo es analizar cómo es efectuada por parte de los socios la coordinación de la empresa cooperativa agraria. Dicha coordinación ha sido analizada a través del análisis de las funciones que deben desarrollar los socios como empresarios. Estas funciones son enumeradas, descritas teóricamente y analizadas a partir de una muestra de cooperativas agrarias pertenecientes a la Denominación de Origen Calificada Rioja. Entre los principales resultados obtenidos cabe destacar que, en la mayoría de los casos analizados, la función de inversor es realizada sin que exista separación con la desempe ada como proveedor; el control formal es ejercido bajo el principio democrático de un hombre un voto; existe poca delegación de las actividades de gestión en una gerencia profesionalizada y cuando esta delegación se produce, no se obtiene niveles de eficiencia significativamente superiores; la organización de actividades muestra una clara especialización en las primeras fases del ciclo productivo y una alta concentración de ventas; por último, la selección de personal es realizada exigiendo unos niveles de cualificación adecuados en cada departamento. / The aim of this work is to analyse how the coordination of the agrarian cooperative firm is brought about by the members. Said coordination has been analysed by means of a study of the functions which members have to develop in their role as managers. These functions have been numbered; theoretically described, and analysed by using a sample of agrarian cooperatives belonging to the Domination of Origin Qualified Rioja. From the principal results obtained, we can highlight the fact that, in most cases analysed, formal control is exercised under the democratic principle, “one-man-one-vote”; where little delegation of management activities exists in professional management and when this delegation occurs, the cooperative does not obtain higher efficiency levels. The organisation of activities shows evident specialization in the first stages of the production cycle and a high sales concentration. Finally, the selection of personnel is made by the appropriate qualification levels required in each department.
Ion-trap simulation of the quantum phase transition in an exactly solvable model of spins coupled to bosons
Gian Luca Giorgi,Simone Paganelli,Fernando Galve
Physics , 2010, DOI: 10.1103/PhysRevA.81.052118
Abstract: It is known that arrays of trapped ions can be used to efficiently simulate a variety of many-body quantum systems. Here, we show how it is possible to build a model representing a spin chain interacting with bosons which is exactly solvable. The exact spectrum of the model at zero temperature and the ground state properties are studied. We show that a quantum phase transition occurs when the coupling between spins and bosons reaches a critical value, which corresponds to a level crossing in the energy spectrum. Once the critical point is reached, the number of bosonic excitations in the ground state, which can be assumed as an order parameter, starts to be different from zero. The population of the bosonic mode is accompanied by a macroscopic magnetization of the spins. This double effect could represent an useful resource for the phase transition detection since a measure on the phonon can give information about the phase of the spin system. A finite temperature phase diagram is also given in the adiabatic regime.
Entanglement dynamics in presence of diversity under decohering environments
Fernando Galve,Gian Luca Giorgi,Roberta Zambrini
Physics , 2010, DOI: 10.1103/PhysRevA.81.062117
Abstract: We study the evolution of entanglement of a pair of coupled, non-resonant harmonic oscillators in contact with an environment. For both the cases of a common bath and of two separate baths for each of the oscillators, a full master equation is provided without rotating wave approximation. This allows us to characterize the entanglement dynamics as a function of the diversity between the oscillators frequencies and their mutual coupling. Also the correlation between the occupation numbers is considered to explore the degree of quantumness of the system. The singular effect of the resonance condition (identical oscillators) and its relationship with the possibility of preserving asymptotic entanglement are discussed. The importance of the bath's memory properties is investigated by comparing Markovian and non-Markovian evolutions.
Bringing entanglement to the high temperature limit
Fernando Galve,Leonardo A. Pachon,David Zueco
Physics , 2010, DOI: 10.1103/PhysRevLett.105.180501
Abstract: We show the existence of an entangled nonequilibrium state at very high temperatures when two linearly coupled harmonic oscillators are parametrically driven and dissipate into two independent heat baths. This result has a twofold meaning: first, it fundamentally shifts the classical-quantum border to temperatures as high as our experimental ability allows us, and second, it can help increase by at least one order of magnitude the temperature at which current experimental setups are operated.
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