25 research outputs found
Weak Chaos in large conservative system -- Infinite-range coupled standard maps
We study, through a new perspective, a globally coupled map system that
essentially interpolates between simple discrete-time nonlinear dynamics and
certain long-range many-body Hamiltonian models. In particular, we exhibit
relevant similarities, namely (i) the existence of long-standing
quasistationary states (QSS), and (ii) the emergence of weak chaos in the
thermodynamic limit, between the present model and the Hamiltonian Mean Field
model, a strong candidate for a nonxtensive statistical mechanical approach.Comment: 6 pages, 2 figures. Corrected typos in equation 4. Changed caption in
Fig. 1. Corrected references 2 and 6. Acknowledgements adde
Multipartite concurrence for identical-fermion systems
We study the problem of detecting multipartite entanglement among indistinguishable fermionic particles. A multipartite concurrence for pure states of N identical fermions, each one having a d-dimensional single-particle Hilbert space, is introduced. Such an entanglement measure, in particular, is optimized for maximally entangled states of three identical fermions that play a role analogous to the usual (qubit) Greenberger-Horne-Zeilinger state. In addition, it is shown that the fermionic multipartite concurrence can be expressed as the mean value of an observable, provided two copies of the composite state are available.Fil: Majtey, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Universidade Federal do Rio de Janeiro; BrasilFil: Bouvrie, P. A.. Centro Brasileiro de Pesquisas Físicas; Brasil. Universidad de Granada; EspañaFil: Valdés Hernández, A.. Universidad Nacional Autónoma de México; MéxicoFil: Plastino, Ángel Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Centro de Bioinvestigaciones (Sede Pergamino); Argentin
Quantum entanglement in exactly soluble atomic models: The Moshinsky model with three electrons, and with two electrons in a uniform magnetic field
We investigate the entanglement-related features of the eigenstates of two exactly soluble atomic models: a one-dimensional three-electron Moshinsky model, and a three-dimensional two-electron Moshinsky system in an external uniform magnetic field. We analytically compute the amount of entanglement exhibited by the wavefunctions corresponding to the ground, first and second excited states of the three-electron model. We found that the amount of entanglement of the system tends to increase with energy, and in the case of excited states we found a finite amount of entanglement in the limit of vanishing interaction. We also analyze the entanglement properties of the ground and first few excited states of the two-electron Moshinsky model in the presence of a magnetic field. The dependence of the eigenstates' entanglement on the energy, as well as its behaviour in the regime of vanishing interaction, are similar to those observed in the three-electron system. On the other hand, the entanglement exhibits a monotonically decreasing behavior with the strength of the external magnetic field. For strong magnetic fields the entanglement approaches a finite asymptotic value that depends on the interaction strength. For both systems studied here we consider a perturbative approach in order to shed some light on the entanglement's dependence on energy and also to clarify the finite entanglement exhibited by excited states in the limit of weak interactions. As far as we know, this is the first work that provides analytical and exact results for the entanglement properties of a three-electron model.Fil: Bouvrie, P. A.. Universidad de Granada; EspañaFil: Majtey, Ana Paula. Universidad de Granada; España. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Plastino, Ángel Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Sánchez Moreno, P.. Universidad de Granada; EspañaFil: Dehesa, J. S.. Universidad de Granada; Españ
Characterization of correlations in two-fermion systems based on measurement induced disturbances
We introduce an approach for the characterization of quantum correlations in two-fermion systems based upon the state disturbances generated by the measurement of “local” observables (that is, quantum observables represented by one-body operators). This approach leads to a concept of quantum correlations in systems of identical fermions different from entanglement.Facultad de Ciencias ExactasCentro Regional de Estudios Genómico
Optimal quantum teleportation protocols for fixed average fidelity
We demonstrate that among all quantum teleportation protocols giving rise to
the same average fidelity, those with aligned Bloch vectors between input and
output states exhibit the minimum average trace distance. This defines optimal
protocols. Furthermore, we show that optimal protocols can be interpreted as
the perfect quantum teleportation protocol under the action of correlated
one-qubit channels. In particular, we focus on the deterministic case, for
which the final Bloch vector length is equal for all measurement outcomes.
Within these protocols, there exists one type that corresponds to the action of
uncorrelated channels: these are depolarizing channels. Thus, we established
the optimal quantum teleportation protocol under a very common experimental
noise.Comment: 9 pages, 1 figur
Wootters’ distance revisited: a new distinguishability criterium
The notion of distinguishability between quantum states has shown to be fundamental in the frame of quantum information theory. In this paper we present a new distinguishability criterium by using a information theoretic quantity: the Jensen-Shannon divergence (JSD). This quantity has several interesting properties, both from a conceptual and a formal point of view. Previous to define this distinguishability criterium, we review some of the most frequently used distances defined over quantum mechanics’ Hilbert space. In this point our main claim is that the JSD can be taken as a unifying distance between quantum states.Instituto de Física La Plat