181 research outputs found
Non-realism : deep thought or a soft option ?
The claim that the observation of a violation of a Bell inequality leads to
an alleged alternative between nonlocality and non-realism is annoying because
of the vagueness of the second term.Comment: 5 page
Violation of Bell's Inequality with Photons from Independent Sources
We report a violation of Bell's inequality using one photon from a parametric
down-conversion source and a second photon from an attenuated laser beam. The
two photons were entangled at a beam splitter using the post-selection
technique of Shih and Alley [Phys. Rev. Lett. 61, 2921 (1988)]. A quantum
interference pattern with a visibility of 91% was obtained using the photons
from these independent sources, as compared with a visibility of 99.4% using
two photons from a central parametric down-conversion source.Comment: 4 pages, 5 figures; minor change
All-Optical Switching Demonstration using Two-Photon Absorption and the Classical Zeno Effect
Low-contrast all-optical Zeno switching has been demonstrated in a silicon
nitride microdisk resonator coupled to a hot atomic vapor. The device is based
on the suppression of the field build-up within a microcavity due to
non-degenerate two-photon absorption. This experiment used one beam in a
resonator and one in free-space due to limitations related to device physics.
These results suggest that a similar scheme with both beams resonant in the
cavity would correspond to input power levels near 20 nW.Comment: 4 pages, 5 figure
Quantum correlations versus Multisimultaneity: an experimental test
Multisimultaneity is a causal model of relativistic quantum physics which
assigns a real time ordering to any set of events, much in the spirit of the
pilot-wave picture. Contrary to standard quantum mechanics, it predicts a
disappearance of the correlations in a Bell-type experiment when both analysers
are in relative motion such that, each one in its own inertial reference frame,
is first to select the output of the photons. We tested this prediction using
acousto-optic modulators as moving beam-splitters and interferometers separated
by 55 m. We didn't observe any disappearance of the correlations, thus refuting
Multisimultaneity.Comment: 4 pages, 3 figures, RevTex 4 versio
Purifying two-bit quantum gates and joint measurements in cavity QED
Using a cavity QED setup we show how to implement a particular joint
measurement on two atoms in a fault tolerant way. Based on this scheme, we
illustrate how to realize quantum communication over a noisy channel when local
operations are subject to errors. We also present a scheme to perform and
purify a universal two-bit gate.Comment: 4 pages RevTeX, 2 figures include
Coherent Atom Interactions Mediated by Dark-State Polaritons
We suggest a technique to induce effective, controllable interactions between
atoms that is based on Raman scattering into an optical mode propagating with a
slow group velocity. The resulting excitation corresponds to the creation of
spin-flipped atomic pairs in a way that is analogous to correlated photon
emission in optical parametric amplification. The technique can be used for
fast generation of entangled atomic ensembles, spin squeezing and applications
in quantum information processing.Comment: 4 pages, 3 figures, minor typos correcte
Are There Quantum Effects Coming from Outside Space-time? Nonlocality, free will and "no many-worlds"
Observing the violation of Bell's inequality tells us something about all
possible future theories: they must all predict nonlocal correlations. Hence
Nature is nonlocal. After an elementary introduction to nonlocality and a brief
review of some recent experiments, I argue that Nature's nonlocality together
with the existence of free will is incompatible with the many-worlds view of
quantum physics.Comment: Talk presented at the meeting "Is Science Compatible with Our Desire
for Freedom?" organised by the Social Trends Institute at the IESE Business
School in Barcelona, Octobre 201
Energy-time entanglement of quasi-particles in solid-state devices
We present a proposal for the experimental observation of energy-time
entanglement of quasi-particles in mesoscopic physics. This type of
entanglement arises whenever correlated particles are produced at the same time
and this time is uncertain in the sense of quantum uncertainty, as has been
largely used in photonics. We discuss its feasibility for electron-hole pairs.
In particular, we argue that the recently fabricated 2DEG-2DHG junctions,
irradiated with a continuous laser, behave as "entanglers" for energy-time
entanglement.Comment: 4 pages, 3 figure
Toxic Exposure of Songbirds to Lead in the Southeast Missouri Lead Mining District
Mining and smelting in the Southeast Missouri Lead Mining District has caused widespread contamination of soils with lead (Pb) and other metals. Soils from three study sites sampled in the district contained from approximately 1,000–3,200 mg Pb/kg. Analyses of earthworms [33–4,600 mg Pb/kg dry weight (dw)] collected in the district showed likely high Pb exposure of songbirds preying on soil organisms. Mean tissue Pb concentrations in songbirds collected from the contaminated sites were greater (p \u3c 0.05) than those in songbirds from reference sites by factors of 8 in blood, 13 in liver, and 23 in kidney. Ranges of Pb concentrations in livers (mg Pb/kg dw) were as follows: northern cardinal (Cardinalis cardinalis) = 0.11–3.0 (reference) and 1.3–30 (contaminated) and American robin (Turdus migratorius) = 0.43–8.5 (reference) and 7.6–72 (contaminated). Of 34 adult and juvenile songbirds collected from contaminated sites, 11 (32 %) had hepatic Pb concentrations that were consistent with adverse physiological effects, 3 (9 %) with systemic toxic effects, and 4 (12 %) with life-threatening toxic effects. Acid-fast renal intranuclear inclusion bodies, which are indicative of Pb poisoning, were detected in kidneys of two robins that had the greatest renal Pb concentrations (952 and 1,030 mg/kg dw). Mean activity of the enzyme delta-aminolevulinic acid dehydratase (ALAD) in red blood cells, a well-established bioindicator of Pb poisoning in birds, was decreased by 58–82 % in songbirds from the mining sites. We conclude that habitats within the mining district with soil Pb concentrations of C1,000 mg Pb/kg are contaminated to the extent that they are exposing ground-feeding songbirds to toxic concentrations of Pb
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