4,941 research outputs found
Trapped-ion quantum error-correcting protocols using only global operations
Quantum error-correcting codes are many-body entangled states that are
prepared and measured using complex sequences of entangling operations. Each
element of such an entangling sequence introduces noise to delicate quantum
information during the encoding or reading out of the code. It is important
therefore to find efficient entangling protocols to avoid the loss of
information. Here we propose an experiment that uses only global entangling
operations to encode an arbitrary logical qubit to either the five-qubit
repetition code or the five-qubit code, with a six-ion Coulomb crystal
architecture in a Penning trap. We show that the use of global operations
enables us to prepare and read out these codes using only six and ten global
entangling pulses, respectively. The proposed experiment also allows the
acquisition of syndrome information during readout. We provide a noise analysis
for the presented protocols, estimating that we can achieve a six-fold
improvement in coherence time with noise as high as on each
entangling operation.Comment: 7 pages, 4 figures, published version, comments are welcom
Latent protein trees
Unbiased, label-free proteomics is becoming a powerful technique for
measuring protein expression in almost any biological sample. The output of
these measurements after preprocessing is a collection of features and their
associated intensities for each sample. Subsets of features within the data are
from the same peptide, subsets of peptides are from the same protein, and
subsets of proteins are in the same biological pathways, therefore, there is
the potential for very complex and informative correlational structure inherent
in these data. Recent attempts to utilize this data often focus on the
identification of single features that are associated with a particular
phenotype that is relevant to the experiment. However, to date, there have been
no published approaches that directly model what we know to be multiple
different levels of correlation structure. Here we present a hierarchical
Bayesian model which is specifically designed to model such correlation
structure in unbiased, label-free proteomics. This model utilizes partial
identification information from peptide sequencing and database lookup as well
as the observed correlation in the data to appropriately compress features into
latent proteins and to estimate their correlation structure. We demonstrate the
effectiveness of the model using artificial/benchmark data and in the context
of a series of proteomics measurements of blood plasma from a collection of
volunteers who were infected with two different strains of viral influenza.Comment: Published in at http://dx.doi.org/10.1214/13-AOAS639 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Probing the 5th Dimension with the QCD String
A salient feature of String/Gauge duality is an extra 5th dimension. Here we
study the effect of confining deformations of AdS5 and compute the spectrum of
a string stretched between infinitely massive quarks and compare it with the
quantum states of the QCD flux as determined by Kuti, Juge and Morningstar in
lattice simulations. In the long flux tube limit the AdS string probes the
metric near the IR cutoff of the 5th dimension with a spectrum approximated by
a Nambu-Goto string in 4-d flat space, whereas at short distance the string
moves to the UV region with a discrete spectrum for pure AdS5. We also review
earlier results on glueballs states and the cross-over between hard and soft
diffractive scattering that support this picture.Comment: 12 pages, 4 figures, invited talk by Brower and Tan at the Eighth
Workshop on Non-Perturbative Quantum Chromodynamcis, June (2004
Bilateral obturator bypass for combined aortic and femorofemoral graft infection
Benedicto GarcĂa, Josep ManuelPla general de la plaça Gal·la PlacĂdia amb la Font de la Blancaneu o Nena amb CĂšrvol, de J.M.Benedicto Garcia, inaugurada el 1947, restaurada per MÂȘ Luisa Aguad
Video Game Telemetry as a Critical Tool in the Study of Complex Skill Learning
Cognitive science has long shown interest in expertise, in part because prediction and control of expert development would have immense practical value. Most studies in this area investigate expertise by comparing experts with novices. The reliance on contrastive samples in studies of human expertise only yields deep insight into development where differences are important throughout skill acquisition. This reliance may be pernicious where the predictive importance of variables is not constant across levels of expertise. Before the development of sophisticated machine learning tools for data mining larger samples, and indeed, before such samples were available, it was difficult to test the implicit assumption of static variable importance in expertise development. To investigate if this reliance may have imposed critical restrictions on the understanding of complex skill development, we adopted an alternative method, the online acquisition of telemetry data from a common daily activity for many: video gaming. Using measures of cognitive-motor, attentional, and perceptual processing extracted from game data from 3360 Real-Time Strategy players at 7 different levels of expertise, we identified 12 variables relevant to expertise. We show that the static variable importance assumption is false - the predictive importance of these variables shifted as the levels of expertise increased - and, at least in our dataset, that a contrastive approach would have been misleading. The finding that variable importance is not static across levels of expertise suggests that large, diverse datasets of sustained cognitive-motor performance are crucial for an understanding of expertise in real-world contexts. We also identify plausible cognitive markers of expertise
COMPARISON OF DRUG EFFECTS ON FIXEDâRATIO PERFORMANCE AND CHAIN PERFORMANCE MAINTAINED UNDER A SECONDâORDER FIXEDâRATIO SCHEDULE
In one component of a multiple schedule, pigeons were required to complete the same fourâresponse chain each session by responding sequentially on three identically lighted keys in the presence of four successively presented colors (chain performance). Food presentation occurred after five completions of the chain (i.e., after 20 correct responses). Errors, such as responding on the center or right key when the left was designated correct, produced a brief timeout but did not reset the chain. In the other component, responding on a single key (lighted white) was maintained by food presentation under a fixedâratio 20 schedule. In general, phencyclidine and dâamphetamine produced doseâdependent decreases in the overall response rates in both components. With pentobarbital, overall rate in each component generally increased at intermediate doses and decreased at higher doses. All three drugs produced doseâdependent disruptive effects on chainâperformance accuracy. Phencyclidine and pentobarbital increased percent errors at doses that had little or no rateâdecreasing effects, whereas dâamphetamine generally increased percent errors only at doses that substantially decreased overall rate. At high doses, all three drugs produced greater disruption of chain performance than of fixedratio performance, as indicated by a slower return to control responding, although the effects of dâamphetamine were less selective than those of phencyclidine or pentobarbital. 1985 Society for the Experimental Analysis of Behavio
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