707 research outputs found
Combined Electric and Magnetic Aharonov-Bohm Effects
It is well-known that the electric and magnetic Aharonov-Bohm effects may be
formally described on equal footing using the four-vector potential in a
relativistic framework. We propose an illustrative manifestation of both
effects in a single configuration, in which the specific path of the charged
particle determines the weight of the electric and magnetic acquired relative
phases. The phases can be distinctively obtained in the Coulomb gauge. The
scheme manifests the pedagogical lesson that though each of the relative phases
is gauge-dependent their sum is gauge-invariant.Comment: 6 figure
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
Quantum Mechanical Realization of a Popescu-Rohrlich Box
We consider quantum ensembles which are determined by pre- and
post-selection. Unlike the case of only pre-selected ensembles, we show that in
this case the probabilities for measurement outcomes at intermediate times
satisfy causality only rarely; such ensembles can in general be used to signal
between causally disconnected regions. We show that under restrictive
conditions, there are certain non-trivial bi-partite ensembles which do satisfy
causality. These ensembles give rise to a violation of the CHSH inequality,
which exceeds the maximal quantum violation given by Tsirelson's bound, , and obtains the Popescu-Rohrlich bound for the maximal
violation, . This may be regarded as an a posteriori
realization of super-correlations, which have recently been termed
Popescu-Rohrlich boxes.Comment: 5 page
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