146 research outputs found
New Phase Transitions in Optimal States for Memory Channels
We investigate the question of optimal input ensembles for memory channels
and construct a rather large class of Pauli channels with correlated noise
which can be studied analytically with regard to the entanglement of their
optimal input ensembles. In a more detailed study of a subclass of these
channels, the complete phase diagram of the two-qubit channel, which shows
three distinct phases is obtained. While increasing the correlation generally
changes the optimal state from separable to maximally entangled states, this is
done via an intermediate region where both separable and maximally entangled
states are optimal. A more concrete model, based on random rotations of the
error operators which mimic the behavior of this subclass of channels is also
presented.Comment: 13 pages, Late
Characterization of qutrit channels in terms of their covariance and symmetry properties
We characterize the completely positive trace-preserving maps on qutrits
(qutrit channels) according to their covariance and symmetry properties. Both
discrete and continuous groups are considered. It is shown how each symmetry
group restricts arbitrariness in the parameters of the channel to a very small
set. Although the explicit examples are related to qutrit channels, the
formalism is sufficiently general to be applied to qudit channels
Transition behavior in the capacity of correlated-noisy channels in arbitrary dimensions
We construct a class of quantum channels in arbitrary dimensions for which
entanglement improves the performance of the channel. The channels have
correlated noise and when the level of correlation passes a critical value we
see a sharp transition in the optimal input states (states which minimize the
output entropy) from separable to maximally entangled states. We show that for
a subclass of channels with some extra conditions, including the examples which
we consider, the states which minimize the output entropy are the ones which
maximize the mutual information.Comment: 11 pages, Latex, 4 figures, Accepted for publication in Physical
Review
Single unconfined compression of cellular dense collagen scaffolds for cartilage and bone tissue engineering
Cell seeded collagen matrix scaffolds have been extensively evaluated recently as potential systems for de-novo tissue regeneration and repair for a variety of tissue types. While collagen gels are biologically excellent as starting point scaffold materials, their use is limited by the lack of cohesive structure and inherently weak mechanical properties due to a high liquid content (>99%). An ingenious method of combining unconfined plastic compression (PC) with capillary action has shown that these scaffolds can be rapidly processed into tissue like structures, which can be immediately implanted into the host[1]. It has been shown that the rapid increase in fibrillar collagen density dramatically enhanced the mechanical properties of such scaffolds thus potentially eliminating the need for long term cellular action. This simple project investigated the effect of single unconfined compression on cartilage-cell seeded collagen matrices in terms of cell viability, proliferation and oxygen consumption
The matrix product representations for all valence bond states
We introduce a simple representation for irreducible spherical tensor
operators of the rotation group of arbitrary integer or half integer rank and
use these tensor operators to construct matrix product states corresponding to
all the variety of valence-bond states proposed in the
Affleck-Kennedy-Lieb-Tasaki (AKLT) construction. These include the fully
dimerized states of arbitrary spins, with uniform or alternating patterns of
spins, which are ground states of Hamiltonians with nearest and next-nearest
neighbor interactions, and the partially dimerized or AKLT/VBS (Valence Bond
Solid) states, which are constructed from them by projection. The latter states
are translation-invariant ground states of Hamiltonians with nearest-neighbor
interactions.Comment: 24 pages, references added, the version which appears in the journa
Antibacterial effect of copper-bearing titanium alloy (Ti-Cu) against Streptococcus mutans and Porphyromonas gingivalis
This work was financially supported by the National Natural Science Foundation (No. 81301329, No. 81271957
and No. 81530051), Joint foundation of Liaoning Province Natural Science Foundation and Shenyang National
Laboratory for materials science (No. 2015021004), Youth Innovation Promotion Association, CAS (No.
2014168), and The Dunhill Medical Trust (R360/0514)
Photon losses depending on polarization mixedness
We introduce a quantum channel describing photon losses depending on the
degree of polarization mixedness. This can be regarded as a model of quantum
channel with correlated errors between discrete and continuous degrees of
freedom. We consider classical information over a continuous alphabet encoded
on weak coherent states as well as classical information over a discrete
alphabet encoded on single photons using dual rail representation. In both
cases we study the one-shot capacity of the channel and its behaviour in terms
of correlation between losses and polarization mixedness
Necessary and sufficient conditions for local creation of quantum discord
We show that a local channel cannot create quantum discord (QD) for zero QD
states of size if and only if either it is a completely decohering
channel or it is a nontrivial isotropic channel. For the qubit case this
propertiy is additionally characteristic to the completely decohering channel
or the commutativity-preserving unital channel. In particular, the exact forms
of the completely decohering channel and the commutativity-preserving unital
qubit channel are proposed. Consequently, our results confirm and improve the
conjecture proposed by X. Hu et al. for the case of and improve the
result proposed by A. Streltsov et al. for the qubit case. Furthermore, it is
shown that a local channel nullifies QD in any state if and only if it is a
completely decohering channel. Based on our results, some protocols of quantum
information processing issues associated with QD, especially for the qubit
case, would be experimentally accessible.Comment: 8 page
Implementing Telemedicine in Medical Emergency Response: Concept of Operation for a Regional Telemedicine Hub
A regional telemedicine hub, providing linkage of a telemedicine command center with an extended network of clinical experts in the setting of a natural or intentional disaster, may facilitate future disaster response and improve patient outcomes. However, the health benefits derived from the use of telemedicine in disaster response have not been quantitatively analyzed. In this paper, we present a general model of the application of telemedicine to disaster response and evaluate a concept of operations for a regional telemedicine hub, which would create distributed surge capacity using regional telemedicine networks connecting available healthcare and telemedicine infrastructures to external expertise. Specifically, we investigate (1) the scope of potential use of telemedicine in disaster response; (2) the operational characteristics of a regional telemedicine hub using a new discrete-event simulation model of an earthquake scenario; and (3) the benefit that the affected population may gain from a coordinated regional telemedicine network
O-C Study of 545 Lunar Occultations from 13 Double Stars
International audienceIn this article, we have studied the reports of lunar occultations by this project observation's teams (named APTO) in comparison with other observations of the objects. Thirteen binary stars were selected for this study. All the previous observations of these stars were also collected. Finally, an analysis of O-C of all reports were performed
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