45 research outputs found
On structural physical approximations and entanglement breaking maps
Very recently a conjecture saying that the so-called structural physical
approximations (SPAa) to optimal positive maps (optimal entanglement witnesses)
give entanglement breaking (EB) maps (separable states) has been posed [J. K.
Korbicz {\it et al.}, Phys. Rev. A {\bf 78}, 062105 (2008)]. The main purpose
of this contribution is to explore this subject. First, we extend the set of
entanglement witnesses (EWs) supporting the conjecture. Then, we ask if SPAs
constructed from other than the depolarizing channel maps also lead to EB maps
and show that in general this is not the case. On the other hand, we prove an
interesting fact that for any positive map there exists an EB channel
such that the SPA of constructed with the aid of is
again an EB channel. Finally, we ask similar questions in the case of
continuous variable systems. We provide a simple way of construction of SPA and
prove that in the case of the transposition map it gives EB channel.Comment: 22 pages, improved version, accepted by Journal of Physics
Prospects for Spin Physics at RHIC
Colliding beams of 70% polarized protons at up to =500 GeV, with
high luminosity, L=2 cmsec, will represent a
new and unique laboratory for studying the proton. RHIC-Spin will be the first
polarized-proton collider and will be capable of copious production of jets,
directly produced photons, and and bosons. Features will include direct
and precise measurements of the polarization of the gluons and of ,
, , and quarks in a polarized proton. Parity violation searches
for physics beyond the standard model will be competitive with unpolarized
searches at the Fermilab Tevatron. Transverse spin will explore transversity
for the first time, as well as quark-gluon correlations in the proton. Spin
dependence of the total cross section and in the Coulomb nuclear interference
region will be measured at collider energies for the first time. These
qualitatively new measurements can be expected to deepen our understanding of
the structure of matter and of the strong interaction.Comment: 51 pages, 22 figures. Scheduled to appear in the Annual Review of
Nuclear and Particle Science Vol. 50, to be published in December 2000 by
Annual Reviews, http://AnnualReviews.or
Recoherence in the entanglement dynamics and classical orbits in the N-atom Jaynes-Cummings model
The rise in linear entropy of a subsystem in the N-atom Jaynes-Cummings model
is shown to be strongly influenced by the shape of the classical orbits of the
underlying classical phase space: we find a one-to-one correspondence between
maxima (minima) of the linear entropy and maxima (minima) of the expectation
value of atomic excitation J_z. Since the expectation value of this operator
can be viewed as related to the orbit radius in the classical phase space
projection associated to the atomic degree of freedom, the proximity of the
quantum wave packet to this atomic phase space borderline produces a maximum
rate of entanglement. The consequence of this fact for initial conditions
centered at periodic orbits in regular regions is a clear periodic recoherence.
For chaotic situations the same phenomenon (proximity of the atomic phase space
borderline) is in general responsible for oscillations in the entanglement
properties.Comment: 15 pages (text), 6 figures; to be published in Physical Review
Schemes of transmission of classical information via quantum channels with many senders: discrete and continuous variables cases
Superadditivity effects in the classical capacity of discrete multi-access
channels (MACs) and continuous variable (CV) Gaussian MACs are analysed. New
examples of the manifestation of superadditivity in the discrete case are
provided including, in particular, a channel which is fully symmetric with
respect to all senders. Furthermore, we consider a class of channels for which
{\it input entanglement across more than two copies of the channels is
necessary} to saturate the asymptotic rate of transmission from one of the
senders to the receiver. The 5-input entanglement of Shor error correction
codewords surpass the capacity attainable by using arbitrary two-input
entanglement for these channels. In the CV case, we consider the properties of
the two channels (a beam-splitter channel and a "non-demolition" XP gate
channel) analyzed in [Czekaj {\it et al.}, Phys. Rev. A {\bf 82}, 020302 (R)
(2010)] in greater detail and also consider the sensitivity of capacity
superadditivity effects to thermal noise. We observe that the estimates of
amount of two-mode squeezing required to achieve capacity superadditivity are
more optimistic than previously reported.Comment: 19 pages, 11 figure
Proposal for measurment of harmonic oscillator Berry phase in ion traps
We propose a scheme for measuring the Berry phase in the vibrational degree
of freedom of a trapped ion. Starting from the ion in a vibrational coherent
state we show how to reverse the sign of the coherent state amplitude by using
a purely geometric phase. This can then be detected through the internal
degrees of freedom of the ion. Our method can be applied to preparation of
Schr\"odinger cat states.Comment: Replaced with revised versio
Violation of multi-particle Bell inequalities for low and high flux parametric amplification using both vacuum and entangled input states
We show how polarisation measurements on the output fields generated by
parametric down conversion will reveal a violation of multi-particle Bell
inequalities, in the regime of both low and high output intensity. In this case
each spatially separated system, upon which a measurement is performed, is
comprised of more than one particle. In view of the formal analogy with spin
systems, the proposal provides an opportunity to test the predictions of
quantum mechanics for spatially separated higher spin states. Here the quantum
behaviour possible even where measurements are performed on systems of large
quantum (particle) number may be demonstrated. Our proposal applies to both
vacuum-state signal and idler inputs, and also to the quantum-injected
parametric amplifier as studied by De Martini et al. The effect of detector
inefficiencies is included.Comment: 12 pages, 12 figure
p73: A Multifunctional Protein in Neurobiology
p73, a transcription factor of the p53 family, plays a key role in many biological processes including neuronal development. Indeed, mice deficient for both TAp73 and ΔNp73 isoforms display neuronal pathologies, including hydrocephalus and hippocampal dysgenesis, with defects in the CA1-CA3 pyramidal cell layers and the dentate gyrus. TAp73 expression increases in parallel with neuronal differentiation and its ectopic expression induces neurite outgrowth and expression of neuronal markers in neuroblastoma cell lines and neural stem cells, suggesting that it has a pro-differentiation role. In contrast, ΔNp73 shows a survival function in mature cortical neurons as selective ΔNp73 null mice have reduced cortical thickness. Recent evidence has also suggested that p73 isoforms are deregulated in neurodegenerative pathologies such as Alzheimer’s disease, with abnormal tau phosphorylation. Thus, in addition to its increasingly accepted contribution to tumorigenesis, the p73 subfamily also plays a role in neuronal development and neurodegeneration
Standardizing Operational Vector Sampling Techniques for Measuring Malaria Transmission Intensity: Evaluation of six Mosquito Collection Methods in Western Kenya.
Operational vector sampling methods lack standardization, making quantitative comparisons of malaria transmission across different settings difficult. Human landing catch (HLC) is considered the research gold standard for measuring human-mosquito contact, but is unsuitable for large-scale sampling. This study assessed mosquito catch rates of CDC light trap (CDC-LT), Ifakara tent trap (ITT), window exit trap (WET), pot resting trap (PRT), and box resting trap (BRT) relative to HLC in western Kenya to 1) identify appropriate methods for operational sampling in this region, and 2) contribute to a larger, overarching project comparing standardized evaluations of vector trapping methods across multiple countries. Mosquitoes were collected from June to July 2009 in four districts: Rarieda, Kisumu West, Nyando, and Rachuonyo. In each district, all trapping methods were rotated 10 times through three houses in a 3 × 3 Latin Square design. Anophelines were identified by morphology and females classified as fed or non-fed. Anopheles gambiae s.l. were further identified as Anopheles gambiae s.s. or Anopheles arabiensis by PCR. Relative catch rates were estimated by negative binomial regression. When data were pooled across all four districts, catch rates (relative to HLC indoor) for An. gambiae s.l (95.6% An. arabiensis, 4.4% An. gambiae s.s) were high for HLC outdoor (RR = 1.01), CDC-LT (RR = 1.18), and ITT (RR = 1.39); moderate for WET (RR = 0.52) and PRT outdoor (RR = 0.32); and low for all remaining types of resting traps (PRT indoor, BRT indoor, and BRT outdoor; RR < 0.08 for all). For Anopheles funestus, relative catch rates were high for ITT (RR = 1.21); moderate for HLC outdoor (RR = 0.47), CDC-LT (RR = 0.69), and WET (RR = 0.49); and low for all resting traps (RR < 0.02 for all). At finer geographic scales, however, efficacy of each trap type varied from district to district. ITT, CDC-LT, and WET appear to be effective methods for large-scale vector sampling in western Kenya. Ultimately, choice of collection method for operational surveillance should be driven by trap efficacy and scalability, rather than fine-scale precision with respect to HLC. When compared with recent, similar trap evaluations in Tanzania and Zambia, these data suggest that traps which actively lure host-seeking females will be most useful for surveillance in the face of declining vector densities
Impact of inactivity and exercise on the vasculature in humans
The effects of inactivity and exercise training on established and novel cardiovascular risk factors are relatively modest and do not account for the impact of inactivity and exercise on vascular risk. We examine evidence that inactivity and exercise have direct effects on both vasculature function and structure in humans. Physical deconditioning is associated with enhanced vasoconstrictor tone and has profound and rapid effects on arterial remodelling in both large and smaller arteries. Evidence for an effect of deconditioning on vasodilator function is less consistent. Studies of the impact of exercise training suggest that both functional and structural remodelling adaptations occur and that the magnitude and time-course of these changes depends upon training duration and intensity and the vessel beds involved. Inactivity and exercise have direct “vascular deconditioning and conditioning” effects which likely modify cardiovascular risk