35,765 research outputs found
Efficient polarization entanglement purification based on parametric down-conversion sources with cross-Kerr nonlinearity
We present a way for entanglement purification based on two parametric
down-conversion (PDC) sources with cross-Kerr nonlinearities. It is comprised
of two processes. The first one is a primary entanglement purification protocol
for PDC sources with nondestructive quantum nondemolition (QND) detectors by
transferring the spatial entanglement of photon pairs to their polarization. In
this time, the QND detectors act as the role of controlled-not (CNot) gates.
Also they can distinguish the photon number of the spatial modes, which
provides a good way for the next process to purify the entanglement of the
photon pairs kept more. In the second process for entanglement purification,
new QND detectors are designed to act as the role of CNot gates. This protocol
has the advantage of high yield and it requires neither CNot gates based on
linear optical elements nor sophisticated single-photon detectors, which makes
it more convenient in practical applications.Comment: 8 pages, 7 figure
Kinematic Basis of Emergent Energetics of Complex Dynamics
Stochastic kinematic description of a complex dynamics is shown to dictate an
energetic and thermodynamic structure. An energy function emerges
as the limit of the generalized, nonequilibrium free energy of a Markovian
dynamics with vanishing fluctuations. In terms of the and its
orthogonal field , a general vector field
can be decomposed into , where
.
The matrix and scalar , two additional characteristics to the
alone, represent the local geometry and density of states intrinsic to
the statistical motion in the state space at . and
are interpreted as the emergent energy and degeneracy of the motion, with an
energy balance equation ,
reflecting the geometrical . The
partition function employed in statistical mechanics and J. W. Gibbs' method of
ensemble change naturally arise; a fluctuation-dissipation theorem is
established via the two leading-order asymptotics of entropy production as
. The present theory provides a mathematical basis for P. W.
Anderson's emergent behavior in the hierarchical structure of complexity
science.Comment: 7 page
Nonlinear reconstruction
We present a direct approach to nonparametrically reconstruct the linear
density field from an observed nonlinear map. We solve for the unique
displacement potential consistent with the nonlinear density and positive
definite coordinate transformation using a multigrid algorithm. We show that we
recover the linear initial conditions up to the nonlinear scale
( for ) with minimal
computational cost. This reconstruction approach generalizes the linear
displacement theory to fully nonlinear fields, potentially substantially
expanding the baryon acoustic oscillations and redshift space distortions
information content of dense large scale structure surveys, including for
example SDSS main sample and 21cm intensity mapping initiatives.Comment: 7 pages, 7 figures, published versio
FDserver: A web service for protein folding research
*Summary:* To facilitate the study of protein folding, we have developed a web service for protein folding rate and folding type prediction as well as for the calculation of a variety of topological parameters of protein structure, which is freely available to the community.
*Availability:* http://sdbi.sdut.edu.cn/FDserve
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