241,542 research outputs found
High-fidelity linear optical quantum computing with polarization encoding
We show that the KLM scheme [Knill, Laflamme and Milburn, Nature {\bf 409},
46] can be implemented using polarization encoding, thus reducing the number of
path modes required by half. One of the main advantages of this new
implementation is that it naturally incorporates a loss detection mechanism
that makes the probability of a gate introducing a non-detected error, when
non-ideal detectors are considered, dependent only on the detector dark-count
rate and independent of its efficiency. Since very low dark-count rate
detectors are currently available, a high-fidelity gate (probability of error
of order conditional on the gate being successful) can be implemented
using polarization encoding. The detector efficiency determines the overall
success probability of the gate but does not affect its fidelity. This can be
applied to the efficient construction of optical cluster states with very high
fidelity for quantum computing.Comment: 12 pages, 7 figures. Improved construction of high-fidelity entangled
ancilla; references adde
Talon cusp affecting primary dentition in two siblings: a case report
The term talon cusp refers to a rare developmental dental anomaly characterized by a cusp-like structure projecting from the cingulum area or cement-enamel junction. This condition can occur in the maxillary and mandibular arches of the primary and permanent dentitions. The purpose of this paper is to report on the presence of talon cusps in the primary dentition of two southern Chinese siblings. The 4 years and 2 months old girl had a talon cusp on her maxillary right primary central incisor, while her 2 years and 9 months old brother had bilateral talon cusps on the maxillary primary central incisors. The presence of this rare dental anomaly in two siblings has scarcely been reported in the literature and this may provide further evidence of a hereditary etiology.Article Link:
http://www.rjme.ro/RJME/resources/files/540113211213.pd
Partial Teleportation of Entanglement in the Noisy Environment
Partial teleportation of entanglement is to teleport one particle of an
entangled pair through a quantum channel. This is conceptually equivalent to
quantum swapping. We consider the partial teleportation of entanglement in the
noisy environment, employing the Werner-state representation of the noisy
channel for the simplicity of calculation. To have the insight of the many-body
teleportation, we introduce the measure of correlation information and study
the transfer of the correlation information and entanglement. We find that the
fidelity gets smaller as the initial-state is entangled more for a given
entanglement of the quantum channel. The entangled channel transfers at least
some of the entanglement to the final state.Comment: 8 pages, 2 figure
Relativistic corrections to the electromagnetic polarizabilities of compound systems
The low-energy amplitude of Compton scattering on the bound state of two
charged particles of arbitrary masses, charges and spins is calculated. A case
in which the bound state exists due to electromagnetic interaction (QED) is
considered. The term, proportional to , is obtained taking into
account the first relativistic correction. It is shown that the complete result
for this correction differs essentially from the commonly used term
, proportional to the r.m.s. charge radius of the system. We
propose that the same situation can take place in the more complicated case of
hadrons.Comment: 19 pages, LaTe
Top quark longitudinal polarization near the threshold in l+ l- annihilation
We show that the longitudinal polarization of the top quarks produced in the
annihilation of e+ e- or mu+ mu- into tbar t at energies near the threshold is
not affected by the large Coulomb-type corrections, which greatly modify the
total cross section. Thus the longitudinal polarization, although small, may
provide an independent information on the mass and the width of the top quark,
largely independent of the uncertainty in alpha_s.Comment: 6 pages, LaTeX, no figures, added references, corrected typo
Quasiclassical Green function in an external field and small-angle scattering
The quasiclassical Green functions of the Dirac and Klein-Gordon equations in
the external electric field are obtained with the first correction taken into
account. The relevant potential is assumed to be localized, while its spherical
symmetry is not required. Using these Green functions, the corresponding wave
functions are found in the approximation similar to the Furry-Sommerfeld-Maue
approximation. It is shown that the quasiclassical Green function does not
coincide with the Green function obtained in the eikonal approximation and has
a wider region of applicability. It is illustrated by the calculation of the
small-angle scattering amplitude for a charged particle and the forward photon
scattering amplitude. For charged particles, the first correction to the
scattering amplitude in the non-spherically symmetric potential is found. This
correction is proportional to the scattering angle. The real part of the
amplitude of forward photon scattering in a screened Coulomb potential is
obtained.Comment: 20 pages, latex, 1 figur
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