8,222 research outputs found
A generalized structure of Bell inequalities for bipartite arbitrary dimensional systems
We propose a generalized structure of Bell inequalities for arbitrary
d-dimensional bipartite systems, which includes the existing two types of Bell
inequalities introduced by Collins-Gisin-Linden-Massar-Popescu [Phys. Rev.
Lett. 88, 040404 (2002)] and Son-Lee-Kim [Phys. Rev. Lett. 96, 060406 (2006)].
We analyze Bell inequalities in terms of correlation functions and joint
probabilities, and show that the coefficients of correlation functions and
those of joint probabilities are in Fourier transform relations. We finally
show that the coefficients in the generalized structure determine the
characteristics of quantum violation and tightness.Comment: 6 pages, 1 figur
High-dimensional Bell test for a continuous variable state in phase space and its robustness to detection inefficiency
We propose a scheme for testing high-dimensional Bell inequalities in phase
space. High-dimensional Bell inequalities can be recast into the forms of a
phase-space version using quasiprobability functions with the complex-valued
order parameter. We investigate their violations for two-mode squeezed states
while increasing the dimension of measurement outcomes, and finally show the
robustness of high-dimensional tests to detection inefficiency.Comment: 8 pages, 2 figures; title and abstract changed, published versio
Ballistic spin field-effect transistors: Multichannel effects
We study a ballistic spin field-effect transistor (SFET) with special
attention to the issue of multi-channel effects. The conductance modulation of
the SFET as a function of the Rashba spin-orbit coupling strength is
numerically examined for the number of channels ranging from a few to close to
100. Even with the ideal spin injector and collector, the conductance
modulation ratio, defined as the ratio between the maximum and minimum
conductances, decays rapidly and approaches one with the increase of the
channel number. It turns out that the decay is considerably faster when the
Rashba spin-orbit coupling is larger. Effects of the electronic coherence are
also examined in the multi-channel regime and it is found that the coherent
Fabry-Perot-like interference in the multi-channel regime gives rise to a
nested peak structure. For a nonideal spin injector/collector structure, which
consists of a conventional metallic ferromagnet-thin insulator-2DEG
heterostructure, the Rashba-coupling-induced conductance modulation is strongly
affected by large resonance peaks that arise from the electron confinement
effect of the insulators. Finally scattering effects are briefly addressed and
it is found that in the weakly diffusive regime, the positions of the resonance
peaks fluctuate, making the conductance modulation signal sample-dependent.Comment: 18 pages, 15 figure
Faithful test of non-local realism with entangled coherent states
We investigate the violation of Leggett's inequality for non-local realism
using entangled coherent states and various types of local measurements. We
prove mathematically the relation between the violation of the
Clauser-Horne-Shimony-Holt form of Bell's inequality and Leggett's one when
tested by the same resources. For Leggett inequalities, we generalize the
non-local realistic bound to systems in Hilbert spaces larger than
bidimensional ones and introduce an optimization technique that allows to
achieve larger degrees of violation by adjusting the local measurement
settings. Our work describes the steps that should be performed to produce a
self-consistent generalization of Leggett's original arguments to
continuous-variable states.Comment: 8 pages, 6 figures, to be published in Phys. Rev.
Effects of squeezing on quantum nonlocality of superpositions of coherent states
We analyze effects of squeezing upon superpositions of coherent states (SCSs)
and entangled coherent states (ECSs) for Bell-inequality tests. We find that
external squeezing can always increase the degrees of Bell violations, if the
squeezing direction is properly chosen, for the case of photon parity
measurements. On the other hand, when photon on/off measurements are used, the
squeezing operation can enhance the degree of Bell violations only for moderate
values of amplitudes and squeezing. We point out that a significant improvement
is required over currently available squeezed SCSs in order to directly
demonstrate a Bell-inequality violation in a real experiment.Comment: 7 pages, 4 figures, accepted for publication in Phys. Rev.
Testing quantum nonlocality by generalized quasiprobability functions
We derive a Bell inequality based on a generalized quasiprobability function
which is parameterized by one non-positive real value. Two types of known Bell
inequalities formulated in terms of the Wigner and Q functions are included as
limiting cases. We investigate violations of our Bell inequalities for single
photon entangled states and two-mode squeezed vacuum states when varying the
detector efficiency. We show that the Bell inequality for the Q function allows
the lowest detection efficiency for violations of local realism.Comment: 6 pages, 3 figure
NOD2/RICK-dependent β-defensin 2 regulation is protective for nontypeable Haemophilus influenzae-induced middle ear infection.
Middle ear infection, otitis media (OM), is clinically important due to the high incidence in children and its impact on the development of language and motor coordination. Previously, we have demonstrated that the human middle ear epithelial cells up-regulate β-defensin 2, a model innate immune molecule, in response to nontypeable Haemophilus influenzae (NTHi), the most common OM pathogen, via TLR2 signaling. NTHi does internalize into the epithelial cells, but its intracellular trafficking and host responses to the internalized NTHi are poorly understood. Here we aimed to determine a role of cytoplasmic pathogen recognition receptors in NTHi-induced β-defensin 2 regulation and NTHi clearance from the middle ear. Notably, we observed that the internalized NTHi is able to exist freely in the cytoplasm of the human epithelial cells after rupturing the surrounding membrane. The human middle ear epithelial cells inhibited NTHi-induced β-defensin 2 production by NOD2 silencing but augmented it by NOD2 over-expression. NTHi-induced β-defensin 2 up-regulation was attenuated by cytochalasin D, an inhibitor of actin polymerization and was enhanced by α-hemolysin, a pore-forming toxin. NOD2 silencing was found to block α-hemolysin-mediated enhancement of NTHi-induced β-defensin 2 up-regulation. NOD2 deficiency appeared to reduce inflammatory reactions in response to intratympanic inoculation of NTHi and inhibit NTHi clearance from the middle ear. Taken together, our findings suggest that a cytoplasmic release of internalized NTHi is involved in the pathogenesis of NTHi infections, and NOD2-mediated β-defensin 2 regulation contributes to the protection against NTHi-induced otitis media
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