41 research outputs found
Entanglement and the Born-Oppenheimer approximation in an exactly solvable quantum many-body system
We investigate the correlations between different bipartitions of an exactly
solvable one-dimensional many-body Moshinsky model consisting of Nn "nuclei"
and Ne "electrons". We study the dependence of entanglement on the
inter-particle interaction strength, on the number of particles, and on the
particle masses. Consistent with kinematic intuition, the entanglement between
two subsystems vanishes when the subsystems have very different masses, while
it attains its maximal value for subsystems of comparable mass. We show how
this entanglement feature can be inferred by means of the Born-Oppenheimer
Ansatz, whose validity and breakdown can be understood from a quantum
information point of view.Comment: Accepted in Eur. Phys. J. D (2014
Bosonic behavior of entangled fermions
Two bound, entangled fermions form a composite boson, which can be treated as
an elementary boson as long as the Pauli principle does not affect the behavior
of many such composite bosons. The departure of ideal bosonic behavior is
quantified by the normalization ratio of multi-composite-boson states. We
derive the two-fermion-states that extremize the normalization ratio for a
fixed single-fermion purity P, and establish general tight bounds for this
indicator. For very small purities, P<1/N^2, the upper and lower bounds
converge, which allows to quantify accurately the departure from perfectly
bosonic behavior, for any state of many composite bosons.Comment: 9 pages, 5 figures, accepted by PR
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
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
Three strongly correlated charged bosons in a one-dimensional harmonic trap: natural orbital occupancies
We study a one-dimensional system composed of three charged bosons confined
in an external harmonic potential. More precisely, we investigate the
ground-state correlation properties of the system, paying particular attention
to the strong-interaction limit. We explain for the first time the nature of
the degeneracies appearing in this limit in the spectrum of the reduced density
matrix. An explicit representation of the asymptotic natural orbitals and their
occupancies is given in terms of some integral equations.Comment: 6 pages, 4 figures, To appear in European Physical Journal
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.Facultad de Ciencias ExactasCentro Regional de Estudios Genómico