5,930 research outputs found
Enhancing entanglement detection of quantum optical frequency combs via stimulated emission
We investigate the performance of a certain nonclassicality identifier,
expressed via integrated second-order intensity moments of optical fields, in
revealing bipartite entanglement of quantum-optical frequency combs (QOFCs),
which are generated in both spontaneous and stimulated parametric
down-conversion processes. We show that, by utilizing that nonclassicality
identifier, one can well identify the entanglement of the QOFC directly from
the experimentally measured intensity moments without invoking any state
reconstruction techniques or homodyne detection. Moreover, we demonstrate that
the stimulated generation of the QOFC improves the entanglement detection of
these fields with the nonclassicality identifier. Additionally, we show that
the nonclassicality identifier can be expressed in a factorized form of
detectors quantum efficiencies and the number of modes, if the QOFC consists of
many copies of the same two-mode twin beam. As an example, we apply the
nonclassicality identifier to two specific types of QOFC, where: (i) the QOFC
consists of many independent two-mode twin beams with non-overlapped spatial
frequency modes, and (ii) the QOFC contains entangled spatial frequency modes
which are completely overlapped, i.e., each mode is entangled with all the
remaining modes in the system. We show that, in both cases, the nonclassicality
identifier can reveal bipartite entanglement of the QOFC including noise, and
that it becomes even more sensitive for the stimulated processes.Comment: 11 p., 8 fig
Correlated bursts and the role of memory range
Inhomogeneous temporal processes in natural and social phenomena have been
described by bursts that are rapidly occurring events within short time periods
alternating with long periods of low activity. In addition to the analysis of
heavy-tailed inter-event time distributions, higher-order correlations between
inter-event times, called correlated bursts, have been studied only recently.
As the possible mechanisms underlying such correlated bursts are far from being
fully understood, we devise a simple model for correlated bursts by using a
self-exciting point process with variable memory range. Here the probability
that a new event occurs is determined by a memory function that is the sum of
decaying memories of the past events. In order to incorporate the noise and/or
limited memory capacity of systems, we apply two memory loss mechanisms, namely
either fixed number or variable number of memories. By using theoretical
analysis and numerical simulations we find that excessive amount of memory
effect may lead to a Poissonian process, which implies that for memory effect
there exists an intermediate range that will generate correlated bursts of
magnitude comparable to empirical findings. Hence our results provide deeper
understanding of how long-range memory affects correlated bursts.Comment: 9 pages, 7 figure
Antiferromagnetic and structural transitions in the superoxide KO2 from first principles: A 2p-electron system with spin-orbital-lattice coupling
KO2 exhibits concomitant antiferromagnetic (AFM) and structural transitions,
both of which originate from the open-shell 2p electrons of O
molecules. The structural transition is accompanied by the coherent tilting of
O molecular axes. The interplay among the spin-orbital-lattice
degrees of freedom in KO2 is investigated by employing the first-principles
electronic structure theory and the kinetic-exchange interaction scheme. We
have shown that the insulating nature of the high symmetry phase of KO2 at high
temperature (T) arises from the combined effect of the spin-orbit coupling and
the strong Coulomb correlation of O 2p electrons. In contrast, for the low
symmetry phase of KO2 at low T with the tilted O molecular axes, the
band gap and the orbital ordering are driven by the combined effects of the
crystal-field and the strong Coulomb correlation. We have verified that the
emergence of the O 2p ferro-orbital ordering is essential to achieve the
observed AFM structure for KO2
The adaptive nature of the bone-periodontal ligament-cementum complex in a ligature-induced periodontitis rat model.
The novel aspect of this study involves illustrating significant adaptation of a functionally loaded bone-PDL-cementum complex in a ligature-induced periodontitis rat model. Following 4, 8, and 15 days of ligation, proinflammatory cytokines (TNF- α and RANKL), a mineral resorption indicator (TRAP), and a cell migration and adhesion molecule for tissue regeneration (fibronectin) within the complex were localized and correlated with changes in PDL-space (functional space). At 4 days of ligation, the functional space of the distal complex was widened compared to controls and was positively correlated with an increased expression of TNF- α. At 8 and 15 days, the number of RANKL(+) cells decreased near the mesial alveolar bone crest (ABC) but increased at the distal ABC. TRAP(+) cells on both sides of the complex significantly increased at 8 days. A gradual change in fibronectin expression from the distal PDL-secondary cementum interfaces through precementum layers was observed when compared to increased and abrupt changes at the mesial PDL-cementum and PDL-bone interfaces in ligated and control groups. Based on our results, we hypothesize that compromised strain fields can be created in a diseased periodontium, which in response to prolonged function can significantly alter the original bone and apical cementum formations
Parity-violating asymmetry in with a pionless effective theory
Nuclear parity violation is studied with polarized neutrons in the
photodisintegration of the deuteron at low energies. A pionless effective field
theory with di-baryon fields is used for the investigation. Hadronic weak
interactions are treated by parity-violating di-baryon-nucleon-nucleon
vertices, which have undetermined coupling contants. A parity-violating
asymmetry in the process is calculated for the incident photon energy up to 30
MeV. If experimental data for the parity-violating asymmetry become available
in the future, we will be able to determine the unknown coupling contants in
the parity-violating vertices.Comment: 4 pages. A contribution to APFB2011, August 22-26, 2011, Seoul, Kore
Eleven-dimensional massless superparticles and matrix theory spin-orbit couplings revisited
The classical probe dynamics of the eleven-dimensional massless
superparticles in the background geometry produced by N source M-momenta is
investigated in the framework of N-sector DLCQ supergravity. We expand the
probe action up to the two fermion terms and find that the fermionic
contributions are the spin-orbit couplings, which precisely agree with the
matrix theory calculations. We comment on the lack of non-perturbative
corrections in the one-loop matrix quantum mechanics effective action and its
compatibility with the supergravity analysis.Comment: 11 pages, Latex, no figure
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