1,393 research outputs found
Error-resistant Single Qubit Gates with Trapped Ions
Coherent operations constitutive for the implementation of single and
multi-qubit quantum gates with trapped ions are demonstrated that are robust
against variations in experimental parameters and intrinsically indeterministic
system parameters. In particular, pulses developed using optimal control theory
are demonstrated for the first time with trapped ions. Their performance as a
function of error parameters is systematically investigated and compared to
composite pulses.Comment: 5 pages 5 figure
Label-Dependencies Aware Recurrent Neural Networks
In the last few years, Recurrent Neural Networks (RNNs) have proved effective
on several NLP tasks. Despite such great success, their ability to model
\emph{sequence labeling} is still limited. This lead research toward solutions
where RNNs are combined with models which already proved effective in this
domain, such as CRFs. In this work we propose a solution far simpler but very
effective: an evolution of the simple Jordan RNN, where labels are re-injected
as input into the network, and converted into embeddings, in the same way as
words. We compare this RNN variant to all the other RNN models, Elman and
Jordan RNN, LSTM and GRU, on two well-known tasks of Spoken Language
Understanding (SLU). Thanks to label embeddings and their combination at the
hidden layer, the proposed variant, which uses more parameters than Elman and
Jordan RNNs, but far fewer than LSTM and GRU, is more effective than other
RNNs, but also outperforms sophisticated CRF models.Comment: 22 pages, 3 figures. Accepted at CICling 2017 conference. Best
Verifiability, Reproducibility, and Working Description awar
Symposium on Event Predictive Cognition
This symposium on Event-Predictive Cognition (EPCog) will scrutinize the apparent strong linkage between events and predictions. Events, characterized as “a segment of time at a given location that is conceived by an observer to have a beginning and an end” (p.3, Zacks & Tversky, 2001), seem to be predictively encoded in our minds, linking and temporarily binding the essential aspects that constitute an event. However, in different disciplines the concept of an event as well as of predictions and predictive encodings has been treated from different perspectives and by means of different paradigms
Is the structure of 42Si understood?
A more detailed test of the implementation of nuclear forces that drive shell
evolution in the pivotal nucleus \nuc{42}{Si} -- going beyond earlier
comparisons of excited-state energies -- is important. The two leading
shell-model effective interactions, SDPF-MU and SDPF-U-Si, both of which
reproduce the low-lying \nuc{42}{Si}() energy, but whose predictions for
other observables differ significantly, are interrogated by the population of
states in neutron-rich \nuc{42}{Si} with a one-proton removal reaction from
\nuc{43}{P} projectiles at 81~MeV/nucleon. The measured cross sections to the
individual \nuc{42}{Si} final states are compared to calculations that combine
eikonal reaction dynamics with these shell-model nuclear structure overlaps.
The differences in the two shell-model descriptions are examined and linked to
predicted low-lying excited states and shape coexistence. Based on the
present data, which are in better agreement with the SDPF-MU calculations, the
state observed at 2150(13)~keV in \nuc{42}{Si} is proposed to be the ()
level.Comment: accepted in Physical Review Letter
Stagnation of GMRES
We study problems for which the iterative method \gmr
for solving linear systems of equations makes no progress
in its initial iterations. Our tool for analysis is
a nonlinear system of equations, the stagnation system,
that characterizes this behavior.
For problems of dimension 2 we can solve this system
explicitly, determining that every choice of eigenvalues
leads to a stagnating problem for eigenvector matrices
that are sufficiently poorly conditioned.
We partially extend this result to higher dimensions
for a class of eigenvector matrices called extreme.
We give necessary and sufficient conditions for stagnation
of systems involving unitary matrices, and show
that if a normal matrix stagnates then so does an entire
family of nonnormal matrices with the same eigenvalues.
Finally, we show that there are real matrices for which
stagnation occurs for certain complex right-hand sides
but not for real ones.
(Also UMIACS-TR-2001-74
Continuous, Semi-discrete, and Fully Discretized Navier-Stokes Equations
The Navier--Stokes equations are commonly used to model and to simulate flow
phenomena. We introduce the basic equations and discuss the standard methods
for the spatial and temporal discretization. We analyse the semi-discrete
equations -- a semi-explicit nonlinear DAE -- in terms of the strangeness index
and quantify the numerical difficulties in the fully discrete schemes, that are
induced by the strangeness of the system. By analyzing the Kronecker index of
the difference-algebraic equations, that represent commonly and successfully
used time stepping schemes for the Navier--Stokes equations, we show that those
time-integration schemes factually remove the strangeness. The theoretical
considerations are backed and illustrated by numerical examples.Comment: 28 pages, 2 figure, code available under DOI: 10.5281/zenodo.998909,
https://doi.org/10.5281/zenodo.99890
Efficient Iterative Algorithms for the Stochastic Finite Element Method with Application to Acoustic Scattering
In this study, we describe the algebraic computations required
to
implement the stochastic finite element method for solving problems in
which uncertainty is restricted to right hand side data coming from
forcing functions or boundary conditions. We show that the solution can be
represented in a compact outer product form which leads to efficiencies in
both work and storage, and we demonstrate that block iterative methods for
algebraic systems with multiple right hand sides can be used to advantage
to compute this solution. We also show how to generate a variety of
statistical quantities from the computed solution. Finally, we examine the
behavior of these statistical quantities in one setting derived from a
model of acoustic scattering. UMIACS-TR-2002-10
Effects of perceived cocaine availability on subjective and objective responses to the drug
<p>Abstract</p> <p>Rationale</p> <p>Several lines of evidence suggest that cocaine expectancy and craving are two related phenomena. The present study assessed this potential link by contrasting reactions to varying degrees of the drug's perceived availability.</p> <p>Method</p> <p>Non-treatment seeking individuals with cocaine dependence were administered an intravenous bolus of cocaine (0.2 mg/kg) under 100% ('unblinded'; N = 33) and 33% ('blinded'; N = 12) probability conditions for the delivery of drug. Subjective ratings of craving, high, rush and low along with heart rate and blood pressure measurements were collected at baseline and every minute for 20 minutes following the infusions.</p> <p>Results</p> <p>Compared to the 'blinded' subjects, their 'unblinded' counterparts had similar craving scores on a multidimensional assessment several hours before the infusion, but reported higher craving levels on a more proximal evaluation, immediately prior to the receipt of cocaine. Furthermore, the 'unblinded' subjects displayed a more rapid onset of high and rush cocaine responses along with significantly higher cocaine-induced heart rate elevations.</p> <p>Conclusion</p> <p>These results support the hypothesis that cocaine expectancy modulates subjective and objective responses to the drug. Provided the important public health policy implications of heavy cocaine use, health policy makers and clinicians alike may favor cocaine craving assessments performed in the settings with access to the drug rather than in more neutral environments as a more meaningful marker of disease staging and assignment to the proper level of care.</p
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