P. Pérez-Fernández
University of Seville
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Featured researches published by P. Pérez-Fernández.
Physical Review A | 2008
A. Relaño; J. M. Arias; J. Dukelsky; J. E. Garcia-Ramos; P. Pérez-Fernández
We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics. We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment. We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition. If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power law.
Physical Review Letters | 2014
V. M. Bastidas; P. Pérez-Fernández; Malte Vogl; Tobias Brandes
We investigate precursors of critical behavior in the quasienergy spectrum due to the dynamical instability in the kicked top. Using a semiclassical approach, we analytically obtain a logarithmic divergence in the density of states, which is analogous to a continuous excited state quantum phase transition in undriven systems. We propose a protocol to observe the cusp behavior of the magnetization close to the critical quasienergy.
Physical Review E | 2017
P. Pérez-Fernández; A. Relaño
We study the thermodynamics of the full version of the Dicke model, including all the possible values of the total angular momentum j, with both microcanonical and canonical ensembles. We focus on both the excited-state quantum phase transition, appearing in the microcanonical description of the maximum angular momentum sector, j=N/2, and the thermal phase transition, which occurs when all the sectors are taken into account. We show that two different features characterize the full version of the Dicke model. If the system is in contact with a thermal bath and is described by means of the canonical ensemble, the parity symmetry becomes spontaneously broken at the critical temperature. In the microcanonical ensemble, and despite that all the logarithmic singularities which characterize the excited-state quantum phase transition are ruled out when all the j sectors are considered, there still exists a critical energy (or temperature) dividing the spectrum into two regions: one in which the parity symmetry can be broken, and another in which this symmetry is always well defined.
Physical Review E | 2014
A. Relaño; J. Dukelsky; P. Pérez-Fernández; J. M. Arias
The ground state and spectral properties of Bose gases in double-well potentials are studied in two different scenarios: (i) an interacting atomic Bose gas, and (ii) a mixture of an atomic gas interacting with diatomic molecules. A ground state second-order quantum phase transition is observed in both scenarios. For large attractive values of the atom-atom interaction, the ground state is degenerate. For repulsive and small attractive interaction, the ground state is not degenerate and is well approximated by a boson coherent state. Both systems depict an excited state quantum phase transition. In both cases, a critical energy separates a region in which all the energy levels are degenerate in pairs, from another region in which there are no degeneracies. For the atomic system, the critical point displays a singularity in the density of states, whereas this behavior is largely smoothed for the mixed atom-molecule system.
Journal of Physics: Conference Series | 2011
F. Pérez-Bernal; O. Álvarez-Bajo; J. M. Arias; M. Carvajal; José Enrique García-Ramos; Danielle Larese; P. Pérez-Fernández
We present a brief review of research topics of current interest that depend on an algebraic approach to molecular bending dynamics. This approach is based on a u(3) spectrum generating algebra. In particular, we briefly present results on three topics: the calculation of finite-size analytical corrections to mean field results, the application of the model to the large-amplitude vibrational bending mode of the NCNCS molecule, and the analysis of the influence of quadratic Casimir operators on excited state quantum phase transitions.
Physical Review A | 2009
P. Pérez-Fernández; A. Relaño; J. M. Arias; J. Dukelsky; J. E. Garcia-Ramos
The decoherence induced on a single qubit by its interaction with the environment is studied. The environment is modeled as a scalar two-level boson system that can go through either first-order or continuous-excited-state quantum phase transitions, depending on the values of the control parameters. A mean-field method based on the Tamm-Damkoff approximation is worked out in order to understand the observed behavior of the decoherence. Only the continuous-excited-state phase transition produces a noticeable effect in the decoherence of the qubit. This is maximal when the system-environment coupling brings the environment to the critical point for the continuous phase transition. In this situation, the decoherence factor (or the fidelity) goes to zero with a finite-size scaling power law.
Physical Review C | 2017
José Enrique García Ramos; P. Pérez-Fernández; José Miguel Arias Carrasco
This work has been supported by the Spanish Ministerio de Econom ia y Competitividad and the European regional development fund (FEDER) under Project No. FIS2014-53448-C2-1-P and FIS2014-53448-C2-2-P
Physical Review C | 2016
J. E. Garcia-Ramos; P. Pérez-Fernández; J. M. Arias; Emilio Freire
This work has been supported by Ministerio de Economia y Competitividad (Spain) and the European Regional Development Fund (FEDER) under projects FIS2014-53448-C2-1-P, and FIS2014-53448-C2-2-P, and by Consejeria de Economia, Innovacion, Ciencia y Empleo de la Junta de Andalucia (Spain) under Group FQM-160, TIC130, and FQM370.
Mathematics in Computer Science | 2016
J. M. Escobar; Juan Núñez; P. Pérez-Fernández
It is well-known that application of invariant functions in various fields of pure or applied mathematics, physics and computer calculations is certainly of interest. In this paper, we study application of the invariant functions of Lie algebras, named
Physical Review A | 2014
V. M. Bastidas; G. Engelhardt; P. Pérez-Fernández; Malte Vogl; Tobias Brandes