6,064 research outputs found
Analysis of the entanglement between two individual atoms using global Raman rotations
Making use of the Rydberg blockade, we generate entanglement between two
atoms individually trapped in two optical tweezers. In this paper we detail the
analysis of the data and show that we can determine the amount of entanglement
between the atoms in the presence of atom losses during the entangling
sequence. Our model takes into account states outside the qubit basis and
allows us to perform a partial reconstruction of the density matrix describing
the two atom state. With this method we extract the amount of entanglement
between pairs of atoms still trapped after the entangling sequence and measure
the fidelity with respect to the expected Bell state. We find a fidelity
for the 62% of atom pairs remaining in the traps at
the end of the entangling sequence
Entanglement of two individual neutral atoms using Rydberg blockade
We report the generation of entanglement between two individual Rb
atoms in hyperfine ground states and which are held in
two optical tweezers separated by 4 m. Our scheme relies on the Rydberg
blockade effect which prevents the simultaneous excitation of the two atoms to
a Rydberg state. The entangled state is generated in about 200 ns using pulsed
two-photon excitation. We quantify the entanglement by applying global Raman
rotations on both atoms. We measure that 61% of the initial pairs of atoms are
still present at the end of the entangling sequence. These pairs are in the
target entangled state with a fidelity of 0.75.Comment: text revised, with additional reference
Entanglement of two individual atoms using the Rydberg blockade
We report on our recent progress on the manipulation of single rubidium atoms
trapped in optical tweezers and the generation of entanglement between two
atoms, each individually trapped in neighboring tweezers. To create an
entangled state of two atoms in their ground states, we make use of the Rydberg
blockade mechanism. The degree of entanglement is measured using global
rotations of the internal states of both atoms. Such internal state rotations
on a single atom are demonstrated with a high fidelity.Comment: Proceeding of the 19th International Conference on Laser Spectroscopy
ICOLS 2009, 7-13 June 2009, Hokkaido, Japa
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Reference-based analysis of lung single-cell sequencing reveals a transitional profibrotic macrophage.
Tissue fibrosis is a major cause of mortality that results from the deposition of matrix proteins by an activated mesenchyme. Macrophages accumulate in fibrosis, but the role of specific subgroups in supporting fibrogenesis has not been investigated in vivo. Here, we used single-cell RNA sequencing (scRNA-seq) to characterize the heterogeneity of macrophages in bleomycin-induced lung fibrosis in mice. A novel computational framework for the annotation of scRNA-seq by reference to bulk transcriptomes (SingleR) enabled the subclustering of macrophages and revealed a disease-associated subgroup with a transitional gene expression profile intermediate between monocyte-derived and alveolar macrophages. These CX3CR1+SiglecF+ transitional macrophages localized to the fibrotic niche and had a profibrotic effect in vivo. Human orthologs of genes expressed by the transitional macrophages were upregulated in samples from patients with idiopathic pulmonary fibrosis. Thus, we have identified a pathological subgroup of transitional macrophages that are required for the fibrotic response to injury
E2 properties of nuclei far from stability and the proton-halo problem of 8B
E2 properties of A=6--10 nuclei, including those of nuclei far from
stability, are studied by a shell-model calculation which
includes E2 core-polarization effects explicitly. The quadrupole moments and
the E2 transition strengths in A=6--10 nuclei are described quite well by the
present calculation. This result indicates that the relatively large value of
the quadrupole moment of B can be understood without introducing the
proton-halo in B. An interesting effect of the
core-polarization is found for effective charges used in the
shell model; although isoscalar effective-charges are almost constant as a
function of nucleus, appreciable variations are needed for isovector
effective-charges which play important roles in nuclei with high
isospin-values.Comment: (LaTeX, 23 pages
The Gelfand spectrum of a noncommutative C*-algebra: a topos-theoretic approach
We compare two influential ways of defining a generalized notion of space.
The first, inspired by Gelfand duality, states that the category of
'noncommutative spaces' is the opposite of the category of C*-algebras. The
second, loosely generalizing Stone duality, maintains that the category of
'pointfree spaces' is the opposite of the category of frames (i.e., complete
lattices in which the meet distributes over arbitrary joins). One possible
relationship between these two notions of space was unearthed by Banaschewski
and Mulvey, who proved a constructive version of Gelfand duality in which the
Gelfand spectrum of a commutative C*-algebra comes out as a pointfree space.
Being constructive, this result applies in arbitrary toposes (with natural
numbers objects, so that internal C*-algebras can be defined). Earlier work by
the first three authors, shows how a noncommutative C*-algebra gives rise to a
commutative one internal to a certain sheaf topos. The latter, then, has a
constructive Gelfand spectrum, also internal to the topos in question. After a
brief review of this work, we compute the so-called external description of
this internal spectrum, which in principle is a fibered pointfree space in the
familiar topos Sets of sets and functions. However, we obtain the external
spectrum as a fibered topological space in the usual sense. This leads to an
explicit Gelfand transform, as well as to a topological reinterpretation of the
Kochen-Specker Theorem of quantum mechanics, which supplements the remarkable
topos-theoretic version of this theorem due to Butterfield and Isham.Comment: 12 page
Digital pulse-shape discrimination of fast neutrons and gamma rays
Discrimination of the detection of fast neutrons and gamma rays in a liquid
scintillator detector has been investigated using digital pulse-processing
techniques. An experimental setup with a 252Cf source, a BC-501 liquid
scintillator detector, and a BaF2 detector was used to collect waveforms with a
100 Ms/s, 14 bit sampling ADC. Three identical ADC's were combined to increase
the sampling frequency to 300 Ms/s. Four different digital pulse-shape analysis
algorithms were developed and compared to each other and to data obtained with
an analogue neutron-gamma discrimination unit. Two of the digital algorithms
were based on the charge comparison method, while the analogue unit and the
other two digital algorithms were based on the zero-crossover method. Two
different figure-of-merit parameters, which quantify the neutron-gamma
discrimination properties, were evaluated for all four digital algorithms and
for the analogue data set. All of the digital algorithms gave similar or better
figure-of-merit values than what was obtained with the analogue setup. A
detailed study of the discrimination properties as a function of sampling
frequency and bit resolution of the ADC was performed. It was shown that a
sampling ADC with a bit resolution of 12 bits and a sampling frequency of 100
Ms/s is adequate for achieving an optimal neutron-gamma discrimination for
pulses having a dynamic range for deposited neutron energies of 0.3-12 MeV. An
investigation of the influence of the sampling frequency on the time resolution
was made. A FWHM of 1.7 ns was obtained at 100 Ms/s.Comment: 26 pages, 14 figures, submitted to Nuclear Instruments and Methods in
Physics Research
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