320 research outputs found
Localizable Entanglement
We consider systems of interacting spins and study the entanglement that can
be localized, on average, between two separated spins by performing local
measurements on the remaining spins. This concept of Localizable Entanglement
(LE) leads naturally to notions like entanglement length and entanglement
fluctuations. For both spin-1/2 and spin-1 systems we prove that the LE of a
pure quantum state can be lower bounded by connected correlation functions. We
further propose a scheme, based on matrix-product states and the Monte Carlo
method, to efficiently calculate the LE for quantum states of a large number of
spins. The virtues of LE are illustrated for various spin models. In
particular, characteristic features of a quantum phase transition such as a
diverging entanglement length can be observed. We also give examples for pure
quantum states exhibiting a diverging entanglement length but finite
correlation length. We have numerical evidence that the ground state of the
antiferromagnetic spin-1 Heisenberg chain can serve as a perfect quantum
channel. Furthermore, we apply the numerical method to mixed states and study
the entanglement as a function of temperature.Comment: 19 pages, modified definition of connected string order parameter,
updated reference
Tripartite to Bipartite Entanglement Transformations and Polynomial Identity Testing
We consider the problem of deciding if a given three-party entangled pure
state can be converted, with a non-zero success probability, into a given
two-party pure state through local quantum operations and classical
communication. We show that this question is equivalent to the well-known
computational problem of deciding if a multivariate polynomial is identically
zero. Efficient randomized algorithms developed to study the latter can thus be
applied to the question of tripartite to bipartite entanglement
transformations
Imaging Neurodegenerative Metabolism in Amyotrophic Lateral Sclerosis with Hyperpolarized [1-13C]pyruvate MRI
The cause of amyotrophic lateral sclerosis (ALS) is still unknown, and consequently, early diagnosis of the disease can be difficult and effective treatment is lacking. The pathology of ALS seems to involve specific disturbances in carbohydrate metabolism, which may be diagnostic and therapeutic targets. Magnetic resonance imaging (MRI) with hyperpolarized [1-(13)C]pyruvate is emerging as a technology for the evaluation of pathway-specific changes in the brain’s metabolism. By imaging pyruvate and the lactate and bicarbonate it is metabolized into, the technology is sensitive to the metabolic changes of inflammation and mitochondrial dysfunction. In this study, we performed hyperpolarized MRI of a patient with newly diagnosed ALS. We found a lateralized difference in [1-(13)C]pyruvate-to-[1-(13)C]lactate exchange with no changes in exchange from [1-(13)C]pyruvate to (13)C-bicarbonate. The 40% increase in [1-(13)C]pyruvate-to-[1-(13)C]lactate exchange corresponded with the patient’s symptoms and presentation with upper-motor neuron affection and cortical hyperexcitability. The data presented here demonstrate the feasibility of performing hyperpolarized MRI in ALS. They indicate potential in pathway-specific imaging of dysfunctional carbohydrate metabolism in ALS, an enigmatic neurodegenerative disease
On Random Unitary Channels
In this article we provide necessary and sufficient conditions for a
completely positive trace-preserving (CPT) map to be decomposable into a convex
combination of unitary maps. Additionally, we set out to define a proper
distance measure between a given CPT map and the set of random unitary maps,
and methods for calculating it. In this way one could determine whether
non-classical error mechanisms such as spontaneous decay or photon loss
dominate over classical uncertainties, for example in a phase parameter. The
present paper is a step towards achieving this goal.Comment: 11 pages, typeset using RevTeX
SBF Distances to Dwarf Elliptical Galaxies in the Sculptor Group
As part of an ongoing search for dwarf elliptical galaxies (dE) in the
vicinity of the Local Group, we acquired deep B and R-band images for five dE
candidates identified in the Sculptor (Scl) group region. We carried out a
surface brightness fluctuation (SBF) analysis on the R-band images to measure
the apparent fluctuation magnitude \bar{m}_R for each dE. Using predictions
from stellar population synthesis models the galaxy distances were determined.
All of these dE candidates turned out to be satellites of Scl group major
members. A redshift measurement of the dE candidate ESO294-010 yielded an
independent confirmation of its group membership: the [OIII] and H
emission lines from a small HII region gave a heliocentric velocity of 117(\pm
5) km s-1, in close agreement with the velocity of its parent galaxy NGC 55
(v_\odot=125 km s-1). The precision of the SBF distances (5 to 10%) contributes
to delineating the cigar-like distribution of the Scl group members, which
extend over distances from 1.7 to 4.4 Mpc and are concentrated in three,
possibly four subclumps. The Hubble diagram for nine Scl galaxies, including
two of our dEs, exhibits a tight linear velocity--distance relation with a
steep slope of 119 km s-1 Mpc-1. The results indicate that gravitational
interaction among the Scl group members plays only a minor role in the dynamics
of the group. However, the Hubble flow of the entire system appears strongly
disturbed by the large masses of our Galaxy and M31 leading to the observed
shearing motion. From the distances and velocities of 49 galaxies located in
the Local Group and towards the Scl group, we illustrate the continuity of the
galaxy distribution which strongly supports the view that the two groups form a
single supergalactic structure.Comment: To appear in The Astronomical Journal, December 1998; 28 pages with
22 figure
Improved Decoupling for 13C coil Arrays Using Non-Conventional Matching and Preamplifier Impedance
Biosynthetic Oligoclonal Antivenom (BOA) for Snakebite and Next-Generation Treatments for Snakebite Victims
Snakebite envenoming is a neglected tropical disease that each year claims the lives of 80,000⁻140,000 victims worldwide. The only effective treatment against envenoming involves intravenous administration of antivenoms that comprise antibodies that have been isolated from the plasma of immunized animals, typically horses. The drawbacks of such conventional horse-derived antivenoms include their propensity for causing allergenic adverse reactions due to their heterologous and foreign nature, an inability to effectively neutralize toxins in distal tissue, a low content of toxin-neutralizing antibodies, and a complex manufacturing process that is dependent on husbandry and procurement of snake venoms. In recent years, an opportunity to develop a fundamentally novel type of antivenom has presented itself. By using modern antibody discovery strategies, such as phage display selection, and repurposing small molecule enzyme inhibitors, next-generation antivenoms that obviate the drawbacks of existing plasma-derived antivenoms could be developed. This article describes the conceptualization of a novel therapeutic development strategy for biosynthetic oligoclonal antivenom (BOA) for snakebites based on recombinantly expressed oligoclonal mixtures of human monoclonal antibodies, possibly combined with repurposed small molecule enzyme inhibitors
- …