12,283 research outputs found
Multipartite entanglement detection in bosons
We propose a simple quantum network to detect multipartite entangled states
of bosons, and show how to implement this network for neutral atoms stored in
an optical lattice. We investigate the special properties of cluster states,
multipartite entangled states and superpositions of distinct macroscopic
quantum states that can be identified by the network.Comment: 4 pages, 2 figure
Scalar Dark Matter in light of LEP and ILC Experiments
In this work we study a scalar field dark matter model with mass of the order
of 100 MeV. We assume dark matter is produced in the process , that, in fact, could be a background for the standard process
extensively studied at LEP. We constrain the
chiral couplings, and , of the dark matter with electrons through an
intermediate fermion of mass GeV and obtain and
for the best fit point of our analysis. We also
analyze the potential of ILC to detect this scalar dark matter for two
configurations: (i) center of mass energy GeV and luminosity
fb, and (ii) center of mass energy TeV
and luminosity fb. The differences of polarized beams
are also explored to better study the chiral couplings.Comment: 15 pages, 6 figures and 1 table. New references added and
improvements in the text. Conclusions unchange
Efficient generation of graph states for quantum computation
We present an entanglement generation scheme which allows arbitrary graph
states to be efficiently created in a linear quantum register via an auxiliary
entangling bus. The dynamics of the entangling bus is described by an effective
non-interacting fermionic system undergoing mirror-inversion in which qubits,
encoded as local fermionic modes, become entangled purely by Fermi statistics.
We discuss a possible implementation using two species of neutral atoms stored
in an optical lattice and find that the scheme is realistic in its requirements
even in the presence of noise.Comment: 4 pages, 3 figures, RevTex 4; v2 - Major changes and new result
Sterile neutrinos, dark matter, and resonant effects in ultra high energy regimes
Interest in light dark matter candidates has recently increased in the
literature; some of these works consider the role of additional neutrinos,
either active or sterile. Furthermore, extragalactic neutrinos have been
detected with energies higher than have ever been reported before. This opens a
new window of opportunities to the study of neutrino properties that were
unreachable up to now. We investigate how an interaction potential between
neutrinos and dark matter might induce a resonant enhancement in the
oscillation probability, an effect that may be tested with future neutrino
data.Comment: 11 pages, 2 figures, to be published in PL
Generation and detection of bound entanglement
We propose a method for the experimental generation of two different families
of bound entangled states of three qubits. Our method is based on the explicit
construction of a quantum network that produces a purification of the desired
state. We also suggest a route for the experimental detection of bound
entanglement, by employing a witness operator plus a test of the positivity of
the partial transposes
A Bayesian estimate of the CMB-large-scale structure cross-correlation
Evidences for late-time acceleration of the Universe are provided by multiple
probes, such as Type Ia supernovae, the cosmic microwave background (CMB) and
large-scale structure (LSS). In this work, we focus on the integrated
Sachs--Wolfe (ISW) effect, i.e., secondary CMB fluctuations generated by
evolving gravitational potentials due to the transition between, e.g., the
matter and dark energy (DE) dominated phases. Therefore, assuming a flat
universe, DE properties can be inferred from ISW detections. We present a
Bayesian approach to compute the CMB--LSS cross-correlation signal. The method
is based on the estimate of the likelihood for measuring a combined set
consisting of a CMB temperature and a galaxy contrast maps, provided that we
have some information on the statistical properties of the fluctuations
affecting these maps. The likelihood is estimated by a sampling algorithm,
therefore avoiding the computationally demanding techniques of direct
evaluation in either pixel or harmonic space. As local tracers of the matter
distribution at large scales, we used the Two Micron All Sky Survey (2MASS)
galaxy catalog and, for the CMB temperature fluctuations, the ninth-year data
release of the Wilkinson Microwave Anisotropy Probe (WMAP9). The results show a
dominance of cosmic variance over the weak recovered signal, due mainly to the
shallowness of the catalog used, with systematics associated with the sampling
algorithm playing a secondary role as sources of uncertainty. When combined
with other complementary probes, the method presented in this paper is expected
to be a useful tool to late-time acceleration studies in cosmology.Comment: 21 pages, 15 figures, 4 tables. We extended the previous analyses
including WMAP9 Q, V and W channels, besides the ILC map. Updated to match
accepted ApJ versio
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