3,304 research outputs found
Quantum trajectories and their statistics for remotely entangled quantum bits
We experimentally and theoretically investigate the quantum trajectories of
jointly monitored transmon qubits embedded in spatially separated microwave
cavities. Using nearly quantum-noise limited superconducting amplifiers and an
optimized setup to reduce signal loss between cavities, we can efficiently
track measurement-induced entanglement generation as a continuous process for
single realizations of the experiment. The quantum trajectories of transmon
qubits naturally split into low and high entanglement classes corresponding to
half-parity collapse. The distribution of concurrence is found at any given
time and we explore the dynamics of entanglement creation in the state space.
The distribution exhibits a sharp cut-off in the high concurrence limit,
defining a maximal concurrence boundary. The most likely paths of the qubits'
trajectories are also investigated, resulting in three probable paths,
gradually projecting the system to two even subspaces and an odd subspace. We
also investigate the most likely time for the individual trajectories to reach
their most entangled state, and find that there are two solutions for the local
maximum, corresponding to the low and high entanglement routes. The theoretical
predictions show excellent agreement with the experimental entangled qubit
trajectory data.Comment: 11 pages and 4 figure
Narrow-band single-photon emission in the near infrared for quantum key distribution
We report on the observation of single colour centers in natural diamond
samples emitting in the near infrared region when optically excited.
Photoluminescence of these single emitters have several striking features, such
as a narrow-band fully polarized emission (FWHM 2 nm) around 780 nm, a short
excited-state lifetime of about 2 ns, and perfect photostability at room
temperature under our excitation conditions. We present a detailed study of
their photophysical properties. Development of a triggered single-photon source
relying on this single colour centre is discussed in the prospect of its
application to quantum key distribution.Comment: 9 page
G92-1119 Rust Diseases of Turfgrass
This NebGuide describes the various rust diseases common to Nebraska and offers suggestions for maintaining a vigorous and disease-resistant lawn.
Rust diseases occur on all turfgrasses; however, most rust problems occur on Kentucky bluegrass, perennial ryegrass, tall fescue and zoysia. In the cool-temperate regions of North America, cool season turfgrasses may suffer severe injury late in summer by attack from one of the rust pathogens. In addition, rust-weakened plants are much more susceptible to injury from environmental stresses and to attack by other turfgrass pathogens
Experimental realization of Wheeler's delayed-choice GedankenExperiment
The quantum "mystery which cannot go away" (in Feynman's words) of
wave-particle duality is illustrated in a striking way by Wheeler's
delayed-choice GedankenExperiment. In this experiment, the configuration of a
two-path interferometer is chosen after a single-photon pulse has entered it :
either the interferometer is \textit{closed} (\textit{i.e.} the two paths are
recombined) and the interference is observed, or the interferometer remains
\textit{open} and the path followed by the photon is measured. We report an
almost ideal realization of that GedankenExperiment, where the light pulses are
true single photons, allowing unambiguous which-way measurements, and the
interferometer, which has two spatially separated paths, produces high
visibility interference. The choice between measuring either the 'open' or
'closed' configuration is made by a quantum random number generator, and is
space-like separated -- in the relativistic sense -- from the entering of the
photon into the interferometer. Measurements in the closed configuration show
interference with a visibility of 94%, while measurements in the open
configuration allow us to determine the followed path with an error probability
lower than 1%
Wheeler's delayed-choice thought experiment: Experimental realization and theoretical analysis
Wheeler has strikingly illustrated the wave-particle duality by the
delayed-choice thought experiment, in which the configuration of a 2-path
interferometer is chosen after a single-photon light-pulsed has entered it. We
present a quantitative theoretical analysis of an experimental realization of
Wheeler's proposal
Generating Entangled Microwave Radiation Over Two Transmission Lines
Using a superconducting circuit, the Josephson mixer, we demonstrate the
first experimental realization of spatially separated two-mode squeezed states
of microwave light. Driven by a pump tone, a first Josephson mixer generates,
out of quantum vacuum, a pair of entangled fields at different frequencies on
separate transmission lines. A second mixer, driven by a -phase shifted
copy of the first pump tone, recombines and disentangles the two fields. The
resulting output noise level is measured to be lower than for vacuum state at
the input of the second mixer, an unambiguous proof of entanglement. Moreover,
the output noise level provides a direct, quantitative measure of entanglement,
leading here to the demonstration of 6 Mebit.s (Mega entangled bits per
second) generated by the first mixer.Comment: 5 pages, 4 figures. Supplementary Information can be found here as an
ancillary fil
Fostering Broad Oral Language Skills in Preschoolers from Low SES Background
Socioeconomic disparities increase the probability that children will enter school behind their more advantaged peers. Early intervention on language skills may enhance language and literacy outcomes, reduce the gap and, eventually, promote school readiness of low-SES (Socioeconomic Status) children. This study aimed to analyze the feasibility and effectiveness of a brief narrative-based intervention (treatment vs. control group) aimed to foster broad oral language skills in preschoolers (N = 69; Mean age = 5.5, SD = 4 months) coming from low-SES families. Moreover, it was analyzed whether children's initial vocabulary mediates the intervention's responsiveness. Results have shown that children in treatment group obtained greater gains than children in control group in almost all intervention-based measures. There is also some evidence for the generalizability of the intervention to other skills not directly trained during the intervention. Moreover, it was found that children's initial vocabulary mediates the intervention's responsiveness showing that children with high vocabulary made greater gains in higher-level components of language comprehension, whereas children with low vocabulary made higher gains in vocabulary. Taken together, our findings suggest that a relatively brief, but quite intensive narrative-based intervention, may produce improvements on broad oral language skills in preschoolers from low-SES backgrounds
Fostering Broad Oral Language Skills in Preschoolers from Low SES Background
Socioeconomic disparities increase the probability that children will enter school behind
their more advantaged peers. Early intervention on language skills may enhance language and literacy
outcomes, reduce the gap and, eventually, promote school readiness of low-SES (Socioeconomic
Status) children. This study aimed to analyze the feasibility and eectiveness of a brief narrative-based
intervention (treatment vs. control group) aimed to foster broad oral language skills in preschoolers
(N = 69; Mean age = 5.5, SD = 4 months) coming from low-SES families. Moreover, it was analyzed
whether children’s initial vocabulary mediates the intervention’s responsiveness. Results have
shown that children in treatment group obtained greater gains than children in control group in
almost all intervention-based measures. There is also some evidence for the generalizability of the
intervention to other skills not directly trained during the intervention. Moreover, it was found that
children’s initial vocabulary mediates the intervention’s responsiveness showing that children with
high vocabulary made greater gains in higher-level components of language comprehension, whereas
children with low vocabulary made higher gains in vocabulary. Taken together, our findings suggest
that a relatively brief, but quite intensive narrative-based intervention, may produce improvements
on broad oral language skills in preschoolers from low-SES backgrounds
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