3,433 research outputs found
Experimental characterization of Gaussian quantum communication channels
We present a full experimental characterization of continuous variable
quantum communication channels established by shared entanglement together with
local operations and classical communication. The resulting teleportation
channel was fully characterized by measuring all elements of the covariance
matrix of the shared two-mode squeezed Gaussian state. From the experimental
data we determined the lower bound to the quantum channel capacity, the
teleportation fidelity of coherent states and the logarithmic negativity and
the purity of the shared state. Additionally, a positive secret key rate was
obtained for two of the established channels.Comment: 9 pages, 4 figures, submitted to Physical Review
Cooking Frequency Associated With Dietary Quality in iCook-4H Youth Participants at Baseline
Background: Increased intakes of ready-made and fast foods paralleled with decreased homemade food consumption have been associated with increased rates of obesity. Researchers have shown associations between cooking self-efficacy (SE) and cooking frequency (CF) with dietary quality and weight status. Some cooking interventions have shown positive associations with dietary outcomes, such as increased fruit and vegetable intake and decreased fast food consumption. There is still much unknown about SE and CF, especially among youth. Objective: Determine baseline SE and CF and the associations with dietary quality and body mass index (BMI) of youth enrolled in iCook 4H. Methods: Youth (n=228, ages 9-10 years) completed online surveys assessing SE, CF, dietary quality, and demographics. Anthropometrics were collected to calculate BMI-for-age percentiles and weight categories. Descriptive statistics were completed for CF, SE, BMI categories, and demographics. Differences in CF and SE by sex, race, and participation in government assistance programs were determined through independent-sample t tests. Pearson correlations were used to assess the association between dietary quality and CF and SE. Associations between CF and dietary quality were assessed further through 2-way analyses of variance (ANOVAs) that included CF and sex and CF and race as independent variables. Associations between SE and CF and BMI were assessed through ANOVAs. Results: Thirty-seven percent of youth were overweight or obese. Females reported significantly higher CF than males (P=.042). Cooking frequency was positively associated with dietary quality (P \u3c .001), but BMI was not associated with dietary quality. SE was not associated with dietary quality or BMI. Conclusion: Based on results, CF was positively associated with dietary quality among youth. More research is needed to assess how different types of cooking relate to diet and BMI. Interventions are needed to determine whether increasing CF leads to better diet outcomes
The Performance and Calibration of the CRAFT Fly's Eye Fast Radio Burst Survey
Since January 2017, the Commensal Real-time ASKAP Fast Transients survey
(CRAFT) has been utilising commissioning antennas of the Australian SKA
Pathfinder (ASKAP) to survey for fast radio bursts (FRBs) in fly's eye mode.
This is the first extensive astronomical survey using phased array feeds
(PAFs), and a total of 20 FRBs have been reported. Here we present a
calculation of the sensitivity and total exposure of this survey, using the
pulsars B1641-45 (J1644-4559) and B0833-45 (J0835-4510, i.e.\ Vela) as
calibrators. The design of the survey allows us to benchmark effects due to PAF
beamshape, antenna-dependent system noise, radio-frequency interference, and
fluctuations during commissioning on timescales from one hour to a year.
Observation time, solid-angle, and search efficiency are calculated as a
function of FRB fluence threshold. Using this metric, effective survey
exposures and sensitivities are calculated as a function of the source counts
distribution. The implied FRB rate is significantly lower than the
\,sky\,day calculated using nominal exposures and
sensitivities for this same sample by \citet{craft_nature}. At the Euclidean
power-law index of , the rate is \,sky\,day above a threshold of \,Jy\,ms, while for the best-fit index for this sample of , it is
\,sky\,day above a threshold of \,Jy\,ms. This strongly suggests that these calculations be performed
for other FRB-hunting experiments, allowing meaningful comparisons to be made
between them.Comment: 21 pages, 15 figures, 2 tables, accepted for publication in PAS
Experimental characterization of frequency dependent squeezed light
We report on the demonstration of broadband squeezed laser beams that show a
frequency dependent orientation of the squeezing ellipse. Carrier frequency as
well as quadrature angle were stably locked to a reference laser beam at
1064nm. This frequency dependent squeezing was characterized in terms of noise
power spectra and contour plots of Wigner functions. The later were measured by
quantum state tomography. Our tomograph allowed a stable lock to a local
oscillator beam for arbitrary quadrature angles with one degree precision.
Frequency dependent orientations of the squeezing ellipse are necessary for
squeezed states of light to provide a broadband sensitivity improvement in
third generation gravitational wave interferometers. We consider the
application of our system to long baseline interferometers such as a future
squeezed light upgraded GEO600 detector.Comment: 8 pages, 8 figure
Cold gas outflows from the Small Magellanic Cloud traced with ASKAP
Feedback from massive stars plays a critical role in the evolution of the
Universe by driving powerful outflows from galaxies that enrich the
intergalactic medium and regulate star formation. An important source of
outflows may be the most numerous galaxies in the Universe: dwarf galaxies.
With small gravitational potential wells, these galaxies easily lose their
star-forming material in the presence of intense stellar feedback. Here, we
show that the nearby dwarf galaxy, the Small Magellanic Cloud (SMC), has atomic
hydrogen outflows extending at least 2 kiloparsecs (kpc) from the star-forming
bar of the galaxy. The outflows are cold, , and may have formed
during a period of active star formation million years (Myr) ago. The
total mass of atomic gas in the outflow is solar masses, , or % of the total atomic gas of the galaxy. The inferred
mass flux in atomic gas alone, , is up to an order of magnitude greater than the star
formation rate. We suggest that most of the observed outflow will be stripped
from the SMC through its interaction with its companion, the Large Magellanic
Cloud (LMC), and the Milky Way, feeding the Magellanic Stream of hydrogen
encircling the Milky Way.Comment: Published in Nature Astronomy, 29 October 2018,
http://dx.doi.org/10.1038/s41550-018-0608-
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