33,050 research outputs found
Generation of Hyperentangled Photons Pairs
We experimentally demonstrate the first quantum system entangled in every
degree of freedom (hyperentangled). Using pairs of photons produced in
spontaneous parametric downconversion, we verify entanglement by observing a
Bell-type inequality violation in each degree of freedom: polarization, spatial
mode and time-energy. We also produce and characterize maximally hyperentangled
states and novel states simultaneously exhibiting both quantum and classical
correlations. Finally, we report the tomography of a 2x2x3x3 system
(36-dimensional Hilbert space), which we believe is the first reported photonic
entangled system of this size to be so characterized.Comment: 5 pages, 3 figures, 1 table, published versio
The London handicap scale: validation of a Yoruba (Nigerian) version among stroke survivors
Objective To evaluate the validity of a Yoruba translated version of the London Handicap Scale (LHS). The LHS is a valid and reliable measure of participation that has been validated in different cultures, but not among Yoruba speaking people of West Africa. Methods A validation study which involved 20 post-stroke patients receiving Physiotherapy on out-patients basis as part of their rehabilitation program. Participants were recruited through purposive sampling techniquebetween February and May, 2008. The English version of the LHS was translated into Yoruba, the language spoken by the Yoruba people of the southwestern Nigeria and other parts of West Africa using a forwardbackward translation process. The English and Yoruba versions of the LHS were completed by the participants with a two-week interval between the administrations of the two scales. Construct validity of theYoruba LHS was assessed by testing its correlation (using Spearman’s rank order correlation) with the English version. Results Total scores on the Yoruba translated version of the LHS correlated significantly with that of the English version (rho = 0.55; p=0.002). Correlation of the domain scores on both scales were significantly correlated with the exception of 2 domains. Conclusion The Yoruba LHS is a valid translation of the English LHS and may be used for the assessment ofparticipation of stroke survivors who comprehend Yoruba language
Electrically detected magnetic resonance of carbon dangling bonds at the Si-face 4H-SiC/SiO interface
SiC based metal-oxide-semiconductor field-effect transistors (MOSFETs) have
gained a significant importance in power electronics applications. However,
electrically active defects at the SiC/SiO interface degrade the ideal
behavior of the devices. The relevant microscopic defects can be identified by
electron paramagnetic resonance (EPR) or electrically detected magnetic
resonance (EDMR). This helps to decide which changes to the fabrication process
will likely lead to further increases of device performance and reliability.
EDMR measurements have shown very similar dominant hyperfine (HF) spectra in
differently processed MOSFETs although some discrepancies were observed in the
measured -factors. Here, the HF spectra measured of different SiC MOSFETs
are compared and it is argued that the same dominant defect is present in all
devices. A comparison of the data with simulated spectra of the C dangling bond
(P) center and the silicon vacancy (V) demonstrates
that the P center is a more suitable candidate to explain the
observed HF spectra.Comment: Accepted for publication in the Journal of Applied Physic
Experiments with hierarchical reinforcement learning of multiple grasping policies
Robotic grasping has attracted considerable interest, but it
still remains a challenging task. The data-driven approach is a promising
solution to the robotic grasping problem; this approach leverages a
grasp dataset and generalizes grasps for various objects. However, these
methods often depend on the quality of the given datasets, which are not
trivial to obtain with sufficient quality. Although reinforcement learning
approaches have been recently used to achieve autonomous collection
of grasp datasets, the existing algorithms are often limited to specific
grasp types. In this paper, we present a framework for hierarchical reinforcement
learning of grasping policies. In our framework, the lowerlevel
hierarchy learns multiple grasp types, and the upper-level hierarchy
learns a policy to select from the learned grasp types according to a point
cloud of a new object. Through experiments, we validate that our approach
learns grasping by constructing the grasp dataset autonomously.
The experimental results show that our approach learns multiple grasping
policies and generalizes the learned grasps by using local point cloud
information
Improving dialysis adherence for high risk patients using automated messaging: Proof of concept
AbstractComorbidities and socioeconomic barriers often limit patient adherence and self-management with hemodialysis. Missed sessions, often associated with communication barriers, can result in emergency dialysis and avoidable hospitalizations. This proof of concept study explored using a novel digital-messaging platform, EpxDialysis, to improve patient-to-dialysis center communication via widely available text messaging and telephone technology. A randomized controlled trial was conducted through Washington University-affiliated hemodialysis centers involving ESRD patients with poor attendance, defined as missing 2–6 sessions over the preceding 12 weeks. A cross-over study design evaluated appointment adherence between intervention and control groups. Comparing nonadherence rates eight weeks prior to enrollment, median appointment adherence after using the system increased by 75%, and median number of unintended hospitalization days fell by 31%. A conservative cost-benefit analysis of EpxDialysis demonstrates a 1:36 savings ratio from appointment adherence. EpxDialysis is a low-risk, cost-effective, intervention for increasing hemodialysis adherence in high-risk patients, especially at centers caring for vulnerable and low-income patients.</jats:p
Measurement of geometric phase for mixed states using single photon interferometry
Geometric phase may enable inherently fault-tolerant quantum computation.
However, due to potential decoherence effects, it is important to understand
how such phases arise for {\it mixed} input states. We report the first
experiment to measure mixed-state geometric phases in optics, using a
Mach-Zehnder interferometer, and polarization mixed states that are produced in
two different ways: decohering pure states with birefringent elements; and
producing a nonmaximally entangled state of two photons and tracing over one of
them, a form of remote state preparation.Comment: To appear in Phys. Rev. Lett. 4 pages, 3 figure
Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant
We here present a high sensitivity gravity-gradiometer based on atom
interferometry. In our apparatus, two clouds of laser-cooled rubidium atoms are
launched in fountain configuration and interrogated by a Raman interferometry
sequence to probe the gradient of gravity field. We recently implemented a
high-flux atomic source and a newly designed Raman lasers system in the
instrument set-up. We discuss the applications towards a precise determination
of the Newtonian gravitational constant G. The long-term stability of the
instrument and the signal-to-noise ratio demonstrated here open interesting
perspectives for pushing the measurement precision below the 100 ppm level
Atom interferometry gravity-gradiometer for the determination of the Newtonian gravitational constant G
We developed a gravity-gradiometer based on atom interferometry for the
determination of the Newtonian gravitational constant \textit{G}. The
apparatus, combining a Rb fountain, Raman interferometry and a juggling scheme
for fast launch of two atomic clouds, was specifically designed to reduce
possible systematic effects. We present instrument performances and show that
the sensor is able to detect the gravitational field induced by source masses.
A discussion of projected accuracy for \textit{G} measurement using this new
scheme shows that the results of the experiment will be significant to
discriminate between previous inconsistent values.Comment: 9 pages,9 figures, Submitte
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