4,851 research outputs found
Hierarchy of inequalities for quantitative duality
We derive different relations quantifying duality in a generic two-way
interferometer. These relations set different upper bounds to the visibility V
of the fringes measured at the output port of the interferometer. A hierarchy
of inequalities is presented which exhibits the influence of the availability
to the experimenter of different sources of which-way information contributing
to the total distinguishability D of the ways. For mixed states and unbalanced
interferometers an inequality is derived, V^2+ Xi^2 \leq 1, which can be more
stringent than the one associated with the distinguishability (V^2+ D^2 \leq
1).Comment: 7 pages, 4 figure
Experimental violation of a spin-1 Bell inequality using maximally-entangled four-photon states
We demonstrate the first experimental violation of a spin-1 Bell inequality.
The spin-1 inequality is a calculation based on the Clauser, Horne, Shimony and
Holt formalism. For entangled spin-1 particles the maximum quantum mechanical
prediction is 2.552 as opposed to a maximum of 2, predicted using local hidden
variables. We obtained an experimental value of 2.27 using the
four-photon state generated by pulsed, type-II, stimulated parametric
down-conversion. This is a violation of the spin-1 Bell inequality by more than
13 standard deviations.Comment: 5 pages, 3 figures, Revtex4. Problem with figures resolve
An AER-Based Actuator Interface for Controlling an Anthropomorphic Robotic Hand
Bio-Inspired and Neuro-Inspired systems or circuits are a
relatively novel approaches to solve real problems by mimicking the biology
in its efficient solutions. Robotic also tries to mimic the biology and
more particularly the human body structure and efficiency of the muscles,
bones, articulations, etc. Address-Event-Representation (AER) is
a communication protocol for transferring asynchronous events between
VLSI chips, originally developed for neuro-inspired processing systems
(for example, image processing). Such systems may consist of a complicated
hierarchical structure with many chips that transmit data among
them in real time, while performing some processing (for example, convolutions).
The information transmitted is a sequence of spikes coded using
high speed digital buses. These multi-layer and multi-chip AER systems
perform actually not only image processing, but also audio processing,
filtering, learning, locomotion, etc. This paper present an AER interface
for controlling an anthropomorphic robotic hand with a neuro-inspired
system.Unión Europea IST-2001-34124 (CAVIAR)Ministerio de Ciencia y Tecnología TIC-2003-08164-C03-0
Decoherence-Free Emergence of Macroscopic Local Realism for entangled photons in a cavity
We investigate the influence of environmental noise on polarization entangled
light generated by parametric emission in a cavity. By adopting a recently
developed separability criterion, we show that: i) self-stimulation may
suppress the detrimental influence of noise on entanglement; ii) when
self-stimulation becomes effective, a classical model of parametric emission
incorporating noise provides the same results of quantum theory for the
expectation values involved in the separability criterion. Moreover we show
that, in the macroscopic limit, it is impossible to observe violations of local
realism with measurements of -particle correlations, whatever n but finite.
These results provide an interesting example of the emergence of macroscopic
local realism in the presence of strong entanglement even in the absence of
decoherence.Comment: 1 figur
Experimental Falsification of Leggett's Non-Local Variable Model
Bell's theorem guarantees that no model based on local variables can
reproduce quantum correlations. Also some models based on non-local variables,
if subject to apparently "reasonable" constraints, may fail to reproduce
quantum physics. In this paper, we introduce a family of inequalities, which
allow testing Leggett's non-local model versus quantum physics, and which can
be tested in an experiment without additional assumptions. Our experimental
data falsify Leggett's model and are in agreement with quantum predictions.Comment: 5 pages, 3 figures, 1 tabl
XMM-Newton Finds That SAX J1750.8-2900 May Harbor the Hottest, Most Luminous Known Neutron Star
We have performed the first sensitive X-ray observation of the low-mass X-ray
binary SAX J1750.8-2900 in quiescence with XMM-Newton. The spectrum was fit to
both a classical black body model, and a non-magnetized, pure hydrogen neutron
star atmosphere model. A power law component was added to these models, but we
found that it was not required by the fits. The distance to SAX J1750.8-2900 is
known to be D = 6.79 kpc from a previous analysis of photospheric radius
expansion bursts. This distance implies a bolometric luminosity (as given by
the NS atmosphere model) of (1.05 +/- 0.12) x 10^34 (D/6.79 kpc)^2 erg s^-1,
which is the highest known luminosity for a NS LMXB in quiescence. One simple
explanation for this surprising result could be that the crust and core of the
NS were not in thermal equilibrium during the observation. We argue that this
was likely not the case, and that the core temperature of the NS in SAX
J1750.8-2900 is unusually high
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