4,634 research outputs found
Generation of maximally entangled states of qudits using twin photons
We report an experiment to generate maximally entangled states of
D-dimensional quantum systems, qudits, by using transverse spatial correlations
of two parametric down-converted photons. Apertures with D-slits in the arms of
the twin fotons define the qudit space. By manipulating the pump beam correctly
the twin photons will pass only by symmetrically opposite slits, generating
entangled states between these differents paths. Experimental results for
qudits with D=4 and D=8 are shown. We demonstrate that the generated states are
entangled states.Comment: 04 pages, 04 figure
Propagation of spatially entangled qudits through free space
We show the propagation of entangled states of high-dimensional quantum
systems. The qudits states were generated using the transverse correlation of
the twin photons produced by spontaneous parametric down-conversion. Their
free-space distribution was performed at the laboratory scale and the
propagated states maintained a high-fidelity with their original form. The use
of entangled qudits allow an increase in the quantity of information that can
be transmitted and may also guarantee more privacy for communicating parties.
Therefore, studies about propagating entangled states of qudits are important
for the effort of building quantum communication networks.Comment: 5 Pages, 4 Figures, REVTeX
Development of Aluminum LEKIDs for Balloon-Borne Far-IR Spectroscopy
We are developing lumped-element kinetic inductance detectors (LEKIDs)
designed to achieve background-limited sensitivity for far-infrared (FIR)
spectroscopy on a stratospheric balloon. The Spectroscopic Terahertz Airborne
Receiver for Far-InfraRed Exploration (STARFIRE) will study the evolution of
dusty galaxies with observations of the [CII] 158 m and other atomic
fine-structure transitions at , both through direct observations of
individual luminous infrared galaxies, and in blind surveys using the technique
of line intensity mapping. The spectrometer will require large format
(1800 detectors) arrays of dual-polarization sensitive detectors with
NEPs of W Hz. The low-volume LEKIDs are fabricated
with a single layer of aluminum (20 nm thick) deposited on a crystalline
silicon wafer, with resonance frequencies of MHz. The inductor is a
single meander with a linewidth of 0.4 m, patterned in a grid to absorb
optical power in both polarizations. The meander is coupled to a circular
waveguide, fed by a conical feedhorn. Initial testing of a small array
prototype has demonstrated good yield, and a median NEP of
W Hz.Comment: accepted for publication in Journal of Low Temperature Physic
Identification of barriers and beliefs influencing engagement by adult and teen Mexican-Americans in oral health behaviors
OBJECTIVE:
To identify barriers and beliefs influencing oral health and dental care-seeking among Mexican-Americans.
RESEARCH DESIGN:
Interviews and Likert-scale survey questions were utilized to explore urgent and preventive dental care-seeking, oral hygiene habits and lifestyle practices. Thirty-three interviews were conducted with 16 adults (ages 33-52), and 17 adolescents (ages 14-19).
RESULTS:
Teens identified the same main barriers to accessing dental care as adults: high cost, financial limitations and lack of insurance. Most Mexican-Americans agreed with the belief that everyone will need urgent dental treatment and the majority believed that going to a dentist in private practice instead of the Emergency Room was important. Although adults recognized the importance of preventive dental care, half reported being unlikely to seek such care while half of teens reported that they were likely to do so. Adults reported relying equally on themselves and on peers to make dental care decisions, while teens mostly depended on others to make decisions about urgent and preventive care. Virtually all respondents believed regular brushing to be important and many flossing too. A major barrier to flossing was being unsure of the proper technique. Another barrier to better oral health was not having seen messages encouraging changes in lifestyle.
CONCLUSIONS:
This study found that Mexican-American teens and adults may experience oral health similarly. Teens do not have more positive oral health beliefs and encounter mostly the same barriers to care as adults
Energy Dissipation and Trapping of Particles Moving on a Rough Surface
We report an experimental, numerical and theoretical study of the motion of a
ball on a rough inclined surface. The control parameters are , the diameter
of the ball, , the inclination angle of the rough surface and ,
the initial kinetic energy. When the angle of inclination is larger than some
critical value, , the ball moves at a constant average
velocity which is independent of the initial conditions. For an angle , the balls are trapped after moving a certain distance. The
dependence of the travelled distances on , and . is
analysed. The existence of two kinds of mechanisms of dissipation is thus
brought to light. We find that for high initial velocities the friction force
is constant. As the velocity decreases below a certain threshold the friction
becomes viscous.Comment: 8 pages RevTeX, 12 Postscript figure
Modificações ambientais causadas pela implantação de Sistemas Agroflorestais em Áreas de Preservação Permanente: marco zero.
Sistemas agroflorestais (SAF) são alternativa para recuperação de Áreas de Preservação Permanente, mantendo-se a área produtiva do ponto de vista ecológico e agrícola. Está sendo feito um estudo, sob princípios da pesquisa-ação participativa, para acompanhamento e avaliação da evolução de SAF sucessionais na APA da Serra da Esperança e caracterização do efeito dos mesmos sobre o ecossistema, bem como sua inserção nos sistemas de produção locais. O objetivo deste trabalho é caracterizar as parcelas anteriormente à implantação dos SAF. Em cada parcela de estudo, em três propriedades de agricultores familiares de Inácio Martins/PR, Brasil, fez-se análises química e física do solo e levantamento florístico. Os solos apresentam baixa fertilidade natural e elevada acidez. O conteúdo de matéria orgânica é elevado e a estrutura apresenta excelentes condições. As parcelas experimentais tem semelhanças quanto à vegetação, entretanto há diferenças em função das práticas agrícolas associadas.Edição dos resumos do 7º Congresso Brasileiro de Agroecologia, 2013, Porto Alegre
Testing the asymptotic relation for period spacings from mixed modes of red giants observed with the Kepler mission
Dipole mixed pulsation modes of consecutive radial order have been detected
for thousands of low-mass red-giant stars with the NASA space telescope Kepler.
Such modes have the potential to reveal information on the physics of the deep
stellar interior. Different methods have been proposed to derive an observed
value for the gravity-mode period spacing, the most prominent one relying on a
relation derived from asymptotic pulsation theory applied to the gravity-mode
character of the mixed modes. Our aim is to compare results based on this
asymptotic relation with those derived from an empirical approach for three
pulsating red-giant stars. We developed a data-driven method to perform
frequency extraction and mode identification. Next, we used the identified
dipole mixed modes to determine the gravity-mode period spacing by means of an
empirical method and by means of the asymptotic relation. In our methodology,
we consider the phase offset, , of the asymptotic
relation as a free parameter. Using the frequencies of the identified dipole
mixed modes for each star in the sample, we derived a value for the
gravity-mode period spacing using the two different methods. These differ by
less than 5%. The average precision we achieved for the period spacing derived
from the asymptotic relation is better than 1%, while that of our data-driven
approach is 3%. Good agreement is found between values for the period spacing
derived from the asymptotic relation and from the empirical method.
Full abstract in PDF file.Comment: 14 pages, 13 figures, accepted for publication in A&
GaAs interfacial self-cleaning by atomic layer deposition
The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial "self-cleaning" is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements
Super-poissonian photon statistics and correlations between pump and probe fields in Electromagnetically Induced Transparency
We have measured the photon statistics of pump and probe beams after
interaction with Rb atoms in a situation of Electromagnetically Induced
Transparency. Both fields present super-poissonian statistics and their
intensities become correlated, in good qualitative agreement with theoretical
predictions in which both fields are treated quantum-mechanically. The
intensity correlations measured are a first step towards the observation of
entanglement between the fields.Comment: 4 pages, two-column, 4 figures, first submitted to PRL on Aug. 6,
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