184 research outputs found
Entanglement of Solitons in the Frenkel-Kontorova Model
We investigate entanglement of solitons in the continuum-limit of the
nonlinear Frenkel-Kontorova chain. We find that the entanglement of solitons
manifests particle-like behavior as they are characterized by localization of
entanglement. The von-Neumann entropy of solitons mixes critical with
noncritical behaviors. Inside the core of the soliton the logarithmic increase
of the entropy is faster than the universal increase of a critical field,
whereas outside the core the entropy decreases and saturates the constant value
of the corresponding massive noncritical field. In addition, two solitons
manifest long-range entanglement that decreases with the separation of the
solitons more slowly than the universal decrease of the critical field.
Interestingly, in the noncritical regime of the Frenkel-Kontorova model,
entanglement can even increase with the separation of the solitons. We show
that most of the entanglement of the so-called internal modes of the solitons
is saturated by local degrees of freedom inside the core, and therefore we
suggest using the internal modes as carriers of quantum information.Comment: 16 pages, 22 figure
Critical and noncritical long range entanglement in the Klein-Gordon field
We investigate the entanglement between two separated segments in the vacuum
state of a free 1D Klein-Gordon field, where explicit computations are
performed in the continuum limit of the linear harmonic chain. We show that the
entanglement, which we measure by the logarithmic negativity, is finite with no
further need for renormalization. We find that the quantum correlations decay
much faster than the classical correlations as in the critical limit long range
entanglement decays exponentially for separations larger than the size of the
segments. As the segments become closer to each other the entanglement diverges
as a power law. The noncritical regime manifests richer behavior, as the
entanglement depends both on the size of the segments and on their separation.
In correspondence with the von Neumann entropy long-range entanglement also
distinguishes critical from noncritical systems
Is Communication Complexity Physical?
Recently, Brassard et. al. conjectured that the fact that the maximal
possible correlations between two non-local parties are the quantum-mechanical
ones is linked to a reasonable restriction on communication complexity. We
provide further support for the conjecture in the multipartite case. We show
that any multipartite communication complexity problem could be reduced to
triviality, had Nature been more non-local than quantum-mechanics by a quite
small gap for any number of parties. Intriguingly, the multipartite
nonlocal-box that we use to show the result corresponds to the generalized Bell
inequality that manifests maximal violation in respect to a local
hidden-variable theory
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