299 research outputs found
Fidelity estimation of quantum states on a silicon photonic chip
As a measure of the 'closeness' of two quantum states, fidelity plays a
fundamental role in quantum information theory. Fidelity estimation protocols
try to strike a balance between information gleaned from an experiment, and the
efficiency of its implementation, in terms of the number of states consumed by
the protocol. Here we adapt a previously reported optimal state verification
protocol (Phys. Rev. Lett. 120, 170502, 2018) for fidelity estimation of
two-qubit states. We demonstrate the protocol experimentally using a
fully-programmable silicon photonic two-qubit chip. Our protocol outputs
significantly smaller error bars of its point estimate in comparison with
another widely-used estimation protocol, showing a clear step forward in the
ability to estimate the fidelity of quantum states produced by a practical
device
Fidelity estimation of quantum states on a silicon photonic chip
As a measure of the 'closeness' of two quantum states, fidelity plays a fundamental role in quantum information theory. Fidelity estimation protocols try to strike a balance between information gleaned from an experiment, and the efficiency of its implementation, in terms of the number of states consumed by the protocol. Here we adapt a previously reported optimal state verification protocol (Phys. Rev. Lett. 120, 170502, 2018) for fidelity estimation of two-qubit states. We demonstrate the protocol experimentally using a fully-programmable silicon photonic two-qubit chip. Our protocol outputs significantly smaller error bars of its point estimate in comparison with another widely-used estimation protocol, showing a clear step forward in the ability to estimate the fidelity of quantum states produced by a practical device
Interpretable Subgroup Discovery in Treatment Effect Estimation with Application to Opioid Prescribing Guidelines
The dearth of prescribing guidelines for physicians is one key driver of the
current opioid epidemic in the United States. In this work, we analyze medical
and pharmaceutical claims data to draw insights on characteristics of patients
who are more prone to adverse outcomes after an initial synthetic opioid
prescription. Toward this end, we propose a generative model that allows
discovery from observational data of subgroups that demonstrate an enhanced or
diminished causal effect due to treatment. Our approach models these
sub-populations as a mixture distribution, using sparsity to enhance
interpretability, while jointly learning nonlinear predictors of the potential
outcomes to better adjust for confounding. The approach leads to
human-interpretable insights on discovered subgroups, improving the practical
utility for decision suppor
Optical pumping NMR in the compensated semiconductor InP:Fe
The optical pumping NMR effect in the compensated semiconductor InP:Fe has
been investigated in terms of the dependences of photon energy (E_p), helicity
(sigma+-), and exposure time (tau_L) of infrared lights. The {31}P and {115}In
signal enhancements show large sigma+- asymmetries and anomalous oscillations
as a function of E_p. We find that (i) the oscillation period as a function of
E_p is similar for {31}P and {115}In and almost field independent in spite of
significant reduction of the enhancement in higher fields. (ii) A
characteristic time for buildup of the {31}P polarization under the light
exposure shows strong E_p-dependence, but is almost independent of sigma+-.
(iii) The buildup times for {31}P and {115}In are of the same order (10^3 s),
although the spin-lattice relaxation times (T_1) are different by more than
three orders of magnitude between them. The results are discussed in terms of
(1) discrete energy spectra due to donor-acceptor pairs (DAPs) in compensated
semiconductors, and (2) interplay between {31}P and dipolar ordered indium
nuclei, which are optically induced.Comment: 8 pages, 6 figures, submitted to Physical Review
Convolution surfaces with varying radius: Formulae for skeletons made of arcs of circles and line segments
International audienceWe develop closed form formulae for the computation of the defining fields of convolutions surfaces. The formulae are obtained for power inverse kernels with skeletons made of line segments or arcs of circle. To obtain the formulae we use Creative Telescoping and describe how this technique can be used for other families of kernels and skeleton primitives. We apply the new formulae to obtain convolution surfaces around skeletons, some of them closed curves. We showcase how the use of arcs of circles greatly improves the visualization of the surface around a general curve compared with a segment based approach
Optical Coherence Tomography Angiography of Optic Disc Perfusion in Glaucoma
Purpose
To compare optic disc perfusion between normal subjects and subjects with glaucoma using optical coherence tomography (OCT) angiography and to detect optic disc perfusion changes in glaucoma.
Design
Observational, cross-sectional study.
Participants
Twenty-four normal subjects and 11 patients with glaucoma were included.
Methods
One eye of each subject was scanned by a high-speed 1050-nm–wavelength swept-source OCT instrument. The split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to compute 3-dimensional optic disc angiography. A disc flow index was computed from 4 registered scans. Confocal scanning laser ophthalmoscopy (cSLO) was used to measure disc rim area, and stereo photography was used to evaluate cup/disc (C/D) ratios. Wide-field OCT scans over the discs were used to measure retinal nerve fiber layer (NFL) thickness.
Main Outcome Measures
Variability was assessed by coefficient of variation (CV). Diagnostic accuracy was assessed by sensitivity and specificity. Comparisons between glaucoma and normal groups were analyzed by Wilcoxon rank-sum test. Correlations among disc flow index, structural assessments, and visual field (VF) parameters were assessed by linear regression.
Results
In normal discs, a dense microvascular network was visible on OCT angiography. This network was visibly attenuated in subjects with glaucoma. The intra-visit repeatability, inter-visit reproducibility, and normal population variability of the optic disc flow index were 1.2%, 4.2%, and 5.0% CV, respectively. The disc flow index was reduced by 25% in the glaucoma group (P = 0.003). Sensitivity and specificity were both 100% using an optimized cutoff. The flow index was highly correlated with VF pattern standard deviation (R[superscript 2] = 0.752, P = 0.001). These correlations were significant even after accounting for age, C/D area ratio, NFL, and rim area.
Conclusions
Optical coherence tomography angiography, generated by the new SSADA, repeatably measures optic disc perfusion and may be useful in the evaluation of glaucoma and glaucoma progression.National Institutes of Health (U.S.) (Grant 1R01 EY023285-01)Rosenbaum's P30EY010572National Institutes of Health (U.S.). Clinical and Translational Science Awards (CTSA) Program (Grant UL1TR000128)Research to Prevent Blindness, Inc. (United States) (Grant R01-EY11289-26)United States. Air Force Office of Scientific Research (FA9550-10-1-0551)German Research Foundation (DFG-HO-1791/11-1)German Research Foundation (DFG-GSC80-SAOT)German Research Foundation (Training Group 1773
Modeling and analysis of energy distribution networks using switched differential systems
It is a pleasure to dedicate this contribution to Prof. Arjan van der Schaft on the occasion of his 60th birthday. We study the dynamics of energy distribution networks consisting of switching power converters and multiple (dis-)connectable modules. We use parsimonious models that deal effectively with the variant complexity of the network and the inherent switching phenomena induced by power converters. We also present the solution to instability problems caused by devices with negative impedance characteristics such as constant power loads. Elements of the behavioral system theory such as linear differential behaviors and quadratic differential forms are crucial in our analysis
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