35,044 research outputs found
Entanglement production due to quench dynamics of an anisotropic XY chain in a transverse field
We compute concurrence and negativity as measures of two-site entanglement
generated by a power-law quench (characterized by a rate 1/tau and an exponent
alpha) which takes an anisotropic XY chain in a transverse field through a
quantum critical point (QCP). We show that only the even-neighbor pairs of
sites get entangled in such a process. Moreover, there is a critical rate of
quench, 1/tau_c, above which no two-site entanglement is generated; the entire
entanglement is multipartite. The ratio of the two-site entanglements between
consecutive even neighbors can be tuned by changing the quench rate. We also
show that for large tau, the concurrence (negativity) scales as sqrt{alpha/tau}
(alpha/tau), and we relate this scaling behavior to defect production by the
quench through a QCP.Comment: 5 pages including 4 figures; added a figure on multipartite
entanglement and some references -- this is the published versio
Exotic hadrons from dynamical clustering of quarks in ultrarelativistic heavy ion collisions
Results from a model study on the formation of exotic quark clusters at the
hadronization stage of a heavy ion collision are presented. The dynamical quark
molecular dynamics (qMD) model which is used is sketched, and results for
exotica made of up to six (anti-)quarks are shown. The second part focuses on
pentaquarks. The rapidity distribution are shown, and the distribution of
strangeness is found to yield an indicator of thermalization and homogenisation
of the deconfined quark system. Relative Theta^+ yields are found to be lower
than thermal model estimates.Comment: 4 pages, 5 figures, to appear in the proceedings of Strangeness in
Quark Matter 2004 (SQM2004), Cape Town, South Africa, 15-20 September 200
-kaon cross section in meson exchange model
We calculate the cross section for the dissociation of by kaons
within the framework of a meson exchange model including anomalous parity
interactions. Off-shell effects at the vertices were handled with QCD sum rule
estimates for the running coupling constants. The total -kaon cross
section was found to be mb for 4.1\leq\sqrt{s}\leq5 \GeV.Comment: 13 pages, 4 eps figure
Distance measures to compare real and ideal quantum processes
With growing success in experimental implementations it is critical to
identify a "gold standard" for quantum information processing, a single measure
of distance that can be used to compare and contrast different experiments. We
enumerate a set of criteria such a distance measure must satisfy to be both
experimentally and theoretically meaningful. We then assess a wide range of
possible measures against these criteria, before making a recommendation as to
the best measures to use in characterizing quantum information processing.Comment: 15 pages; this version in line with published versio
Coherently controlled entanglement generation in a binary Bose-Einstein condensate
Considering a two-component Bose-Einstein condensate in a double-well
potential, a method to generate a Bell state consisting of two spatially
separated condensates is suggested. For repulsive interactions, the required
tunnelling control is achieved numerically by varying the amplitude of a
sinusoidal potential difference between the wells. Both numerical and
analytical calculations reveal the emergence of a highly entangled mesoscopic
state.Comment: 6 pages, 6 figures, epl2.cl
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