908 research outputs found
Bipartite Bell inequalities for hyperentangled states
We show that bipartite Bell inequalities based on the Einstein-Podolsky-Rosen
criterion for elements of reality and derived from the properties of some
hyperentangled states allow feasible experimental verifications of the fact
that quantum nonlocality grows exponentially with the size of the subsystems,
and Bell loophole-free tests with currently available photodetection
efficiencies.Comment: REVTeX4, 5 page
Loophole-free Bell's experiment and two-photon all-versus-nothing violation of local realism
We introduce an all-versus-nothing proof of impossibility of
Einstein-Podolsky-Rosen's local elements of reality for two photons entangled
both in polarization and path degrees of freedom, which leads to a Bell's
inequality where the classical bound is 8 and the quantum prediction is 16. A
simple estimation of the detection efficiency required to close the detection
loophole using this proof gives eta > 0.69. This efficiency is lower than that
required for previous proposals.Comment: REVTeX4, 4 page
Two-player quantum pseudo-telepathy based on recent all-versus-nothing violations of local realism
We introduce two two-player quantum pseudo-telepathy games based on two
recently proposed all-versus-nothing (AVN) proofs of Bell's theorem [A.
Cabello, Phys. Rev. Lett. 95, 210401 (2005); Phys. Rev. A 72, 050101(R)
(2005)]. These games prove that Broadbent and Methot's claim that these AVN
proofs do not rule out local-hidden-variable theories in which it is possible
to exchange unlimited information inside the same light-cone (quant-ph/0511047)
is incorrect.Comment: REVTeX4, 5 page
Efecto trichomonicida, in vitro, de Dimetil Sulfoxido, Yoduro de Sodio, Tripaflavina, Bovoflavina y Lugol
Experimental noise-resistant Bell-inequality violations for polarization-entangled photons
We experimentally demonstrate that violations of Bell's inequalities for
two-photon polarization-entangled states with colored noise are extremely
robust, whereas this is not the case for states with white noise. Controlling
the amount of noise by using the timing compensation scheme introduced by Kim
et al. [Phys. Rev. A 67, 010301(R) (2003)], we have observed violations even
for states with very high noise, in excellent agrement with the predictions of
Cabello et al. [Phys. Rev. A 72, 052112 (2005)].Comment: REVTeX4, 5 pages, 4 figure
Proposed experiment to test the bounds of quantum correlations
Clauser-Horne-Shimony-Holt inequality can give values between the classical
bound, 2, and Tsirelson's bound, 2 \sqrt 2. However, for a given set of local
observables, there are values in this range which no quantum state can attain.
We provide the analytical expression for the corresponding bound for a
parametrization of the local observables introduced by Filipp and Svozil, and
describe how to experimentally trace it using a source of singlet states. Such
an experiment will be useful to identify the origin of the experimental errors
in Bell's inequality-type experiments and could be modified to detect
hypothetical correlations beyond those predicted by quantum mechanics.Comment: REVTeX4, 4 pages, 2 figure
Multiparty multilevel Greenberger-Horne-Zeilinger states
The proof of Bell's theorem without inequalities by Greenberger, Horne, and
Zeilinger (GHZ) is extended to multiparticle multilevel systems. The proposed
procedure generalizes previous partial results and provides an operational
characterization of the so-called GHZ states for multiparticle multilevel
systems.Comment: REVTeX, 5 pages, 1 figur
Quantum correlations are not local elements of reality
I show a situation of multiparticle entanglement which cannot be explained in
the framework of an interpretation of quantum mechanics recently proposed by
Mermin. This interpretation is based on the assumption that correlations
between subsystems of an individual isolated composed quantum system are real
objective local properties of that system.Comment: REVTeX, 3 page
Minimum detection efficiency for a loophole-free atom-photon Bell experiment
In Bell experiments, one problem is to achieve high enough photodetection to
ensure that there is no possibility of describing the results via a local
hidden-variable model. Using the Clauser-Horne inequality and a two-photon
non-maximally entangled state, a photodetection efficiency higher than 0.67 is
necessary. Here we discuss atom-photon Bell experiments. We show that, assuming
perfect detection efficiency of the atom, it is possible to perform a
loophole-free atom-photon Bell experiment whenever the photodetection
efficiency exceeds 0.50.Comment: REVTeX4, 4 pages, 1 figur
"All versus nothing" inseparability for two observers
A recent proof of Bell's theorem without inequalities [A. Cabello, Phys. Rev.
Lett. 86, 1911 (2001)] is formulated as a Greenberger-Horne-Zeilinger-like
proof involving just two observers. On one hand, this new approach allows us to
derive an experimentally testable Bell inequality which is violated by quantum
mechanics. On the other hand, it leads to a new state-independent proof of the
Kochen-Specker theorem and provides a wider perspective on the relations
between the major proofs of no-hidden-variables.Comment: REVTeX, 4 page
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