4,899 research outputs found
Quantum correlations from local amplitudes and the resolution of the Einstein-Podolsky-Rosen nonlocality puzzle
The Einstein-Podolsky-Rosen nonlocality puzzle has been recognized as one of
the most important unresolved issues in the foundational aspects of quantum
mechanics. We show that the problem is resolved if the quantum correlations are
calculated directly from local quantities which preserve the phase information
in the quantum system. We assume strict locality for the probability amplitudes
instead of local realism for the outcomes, and calculate an amplitude
correlation function.Then the experimentally observed correlation of outcomes
is calculated from the square of the amplitude correlation function. Locality
of amplitudes implies that the measurement on one particle does not collapse
the companion particle to a definite state. Apart from resolving the EPR
puzzle, this approach shows that the physical interpretation of apparently
`nonlocal' effects like quantum teleportation and entanglement swapping are
different from what is usually assumed. Bell type measurements do not change
distant states. Yet the correlations are correctly reproduced, when measured,
if complex probability amplitudes are treated as the basic local quantities. As
examples we discuss the quantum correlations of two-particle maximally
entangled states and the three-particle GHZ entangled state.Comment: Std. Latex, 11 pages, 1 table. Prepared for presentation at the
International Conference on Quantum Optics, ICQO'2000, Minsk, Belaru
Envelope frequency following responses are stronger for high-pass than low-pass filtered vowels
Background: To assess hearing in response to speech, the envelope frequency following response (FFR) can be observed at the fundamental frequency of a vowel stimulus, and its harmonics. FFRs are complex non-linear phenomena, which require better understanding for allowing robust inferences on the assessment of hearing and hearing aid fitting.
Objectives: To evaluate the effect of stimulus bandwidth on FFR detection rates using filtered vowel stimuli with equal sound levels.
Design: FFRs were collected whilst presenting repeated vowels (in consonant-vowel-consonant format) filtered into different bandwidths. Eighty stimuli per word were presented at 70 dB SPL LAeq through insert earphones with an inter-stimulus interval of 1s. Responses were detected using frequency-domain Hotellingâs T2 (HT2) tests for individual multiples of the fundamental frequency (F0) and for combinations of F0 multiples.
Study Sample: Eleven native English-speaking subjects with normal hearing thresholds.
Results: Average detection rates are highest (69%) with stimuli high-pass filtered >1000 Hz, and significantly lower for low-pass filtered stimuli (40%).
Conclusion: High-pass filtered vowels elicit stronger FFRs than low-pass filtered vowels at the same dB SPL LAeq. For testing hearing using band-limited speech, filtering effects (due to hearing loss, hearing aid setting or stimulus choice) on responses must be considered
Generalized Quantum Theory: Overview and Latest Developments
The main formal structures of Generalized Quantum Theory are summarized.
Recent progress has sharpened some of the concepts, in particular the notion of
an observable, the action of an observable on states (putting more emphasis on
the role of proposition observables), and the concept of generalized
entanglement. Furthermore, the active role of the observer in the structure of
observables and the partitioning of systems is emphasized.Comment: 14 pages, update in reference
Extensive winter subglacial water storage beneath the Greenland Ice Sheet
This is the final version of the article. Available from AGU via the DOI in this record.Surface meltwater that reaches the base of the Greenland Ice Sheet exerts a fundamental impact on ice flow, but observations of catchment-wide movement and distribution of subglacial water remain limited. Using radar-sounding data from two seasons, we identify the seasonal distribution of subglacial water in western Greenland. Our analysis provides evidence of widespread subglacial water storage beneath Greenland in the wintertime. The winter storage is located primarily on bedrock ridges with higher bed elevations in excess of 200 m. During the melt season water moves to the subglacial troughs. This inverse relationship with topography indicates that the material properties of the glacier bed strongly influence subglacial drainage development. Both the spatial variations in bed properties and the initial state of the subglacial hydrology system at the start of the melt season lead to differing glacier dynamical responses to surface melting across the Greenland Ice Sheet.W.C. is a recipient of the NASA Earth and
Space Science Fellowship. D.M.S. is
supported by a grant from the NASA
Cryospheric Sciences Program. H.S. is
supported by grants from the NASA
Cryospheric Sciences and Sea Level Rise
Programs. T.T.C and R.E.B are supported
by grants from National Science
Foundation (NSF) and NASA
Cryospheric Sciences. S.P. is supported
by the Natural Environment Research
Councilâs Centre for Polar Observatio
Stratigraphic hierarchy and threeâdimensional evolution of an exhumed submarine slope channel system
Submarine slope channel systems have complicated threeâdimensional geometries and facies distributions, which are challenging to resolve using subsurface data. Outcrop analogues can provide subâseismicâscale detail, although most exhumed systems only afford twoâdimensional constraints on the depositional architecture. A rare example of an accessible fineâgrained slope channel complex set situated in a tectonically quiescent basin that offers seismicâscale, downâdip and acrossâstrike exposures is the Klein Hangklip area, TanquaâKaroo Basin, South Africa. This study investigates the threeâdimensional architecture of this channel complex set to characterise the stratigraphic evolution of a submarine channelâfill and the implications this has for both sediment transport to the deepâoceans and reservoir quality distribution. Correlated sedimentary logs and mapping of key surfaces across a 3 km2 area reveal that: (i) the oldest channel elements in channel complexes infill relatively deep channel cuts and have low aspectâratios. Later channel elements are bound by comparatively flat erosion surfaces and have high aspectâratios; (ii) facies changes across depositional strike are consistent and predictable; conversely, facies change in successive down depositional dip positions indicating longitudinal variability in depositional processes; (iii) stratigraphic architecture is consistent and predictable at seismicâscale both downâdip and acrossâstrike in threeâdimensions; (iv) channelâbaseâdeposits exhibit spatial heterogeneity on one to hundreds of metres lengthâscales, which can inhibit accurate recognition and interpretations drawn from oneâdimensional or limited twoâdimensional datasets; and (v) channelâbaseâdeposit character is linked to sediment bypass magnitude and longevity, which suggests that timeâpartitioning is biased towards conduit excavation and maintenance rather than the fillâphase. The data provide insights into the stratigraphic evolution and architecture of slope channelâfills on fineâgrained continental margins and can be utilised to improve predictions derived from lower resolution and oneâdimensional well data
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Charge Transfer in Single Chains of a Donor-Acceptor Conjugated Tri-Block Copolymer.
The photophysics of a conjugated triblock copolymer comprising poly(9,9-dioctylfluorene-co-bis-N,N'-(4-methylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFM) electron donor and poly(4-(9,9-dioctyl-9H-fluoren-2-yl)benzo[c][1,2,5]-thiadiazole) (F8BT) electron acceptor blocks has been studied in solution, in films, and as single chains. While an additional long-wavelength emission apparent in neat films of the copolymer is attributed to interchain exciplex formation, no such long-wavelength emission is apparent in solution or from single molecules. However, in these cases, time-resolved fluorescence measurements indicate the presence of a delayed fluorescence. The kinetics of the delayed emission can be interpreted in terms of an equilibrium between a locally excited and a charge-transfer state at the interface of the copolymer block components. Rate constants and thermodynamic quantities associated with these processes have been evaluated. The single-molecule results allow the assignment of an intramolecular charge-transfer state in an isolated conjugated block copolymer chain.We thank the Australian Research Council (ARC) for financial support of this research through grants
DP0986166, LE100100131 and LE110100161. ENH acknowledges an Australian Postgraduate Award. We acknowledge Sam Ashworth for technical assistance with data collection. NCG is grateful to the
School of Chemistry, The University of Melbourne for a Wilsmore Fellowship, and to Queenâs College,
Melbourne for a Sugden Fellowship.This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/jp510769p
An experimental test of non-local realism
Most working scientists hold fast to the concept of 'realism' - a viewpoint
according to which an external reality exists independent of observation. But
quantum physics has shattered some of our cornerstone beliefs. According to
Bell's theorem, any theory that is based on the joint assumption of realism and
locality (meaning that local events cannot be affected by actions in space-like
separated regions) is at variance with certain quantum predictions. Experiments
with entangled pairs of particles have amply confirmed these quantum
predictions, thus rendering local realistic theories untenable. Maintaining
realism as a fundamental concept would therefore necessitate the introduction
of 'spooky' actions that defy locality. Here we show by both theory and
experiment that a broad and rather reasonable class of such non-local realistic
theories is incompatible with experimentally observable quantum correlations.
In the experiment, we measure previously untested correlations between two
entangled photons, and show that these correlations violate an inequality
proposed by Leggett for non-local realistic theories. Our result suggests that
giving up the concept of locality is not sufficient to be consistent with
quantum experiments, unless certain intuitive features of realism are
abandoned.Comment: Minor corrections to the manuscript, the final inequality and all its
conclusions do not change; description of corrections (Corrigendum) added as
new Appendix III; Appendix II replaced by a shorter derivatio
A biophysical model of cell adhesion mediated by immunoadhesin drugs and antibodies
A promising direction in drug development is to exploit the ability of
natural killer cells to kill antibody-labeled target cells. Monoclonal
antibodies and drugs designed to elicit this effect typically bind cell-surface
epitopes that are overexpressed on target cells but also present on other
cells. Thus it is important to understand adhesion of cells by antibodies and
similar molecules. We present an equilibrium model of such adhesion,
incorporating heterogeneity in target cell epitope density and epitope
immobility. We compare with experiments on the adhesion of Jurkat T cells to
bilayers containing the relevant natural killer cell receptor, with adhesion
mediated by the drug alefacept. We show that a model in which all target cell
epitopes are mobile and available is inconsistent with the data, suggesting
that more complex mechanisms are at work. We hypothesize that the immobile
epitope fraction may change with cell adhesion, and we find that such a model
is more consistent with the data. We also quantitatively describe the parameter
space in which binding occurs. Our results point toward mechanisms relating
epitope immobility to cell adhesion and offer insight into the activity of an
important class of drugs.Comment: 13 pages, 5 figure
Decision Making for Inconsistent Expert Judgments Using Negative Probabilities
In this paper we provide a simple random-variable example of inconsistent
information, and analyze it using three different approaches: Bayesian,
quantum-like, and negative probabilities. We then show that, at least for this
particular example, both the Bayesian and the quantum-like approaches have less
normative power than the negative probabilities one.Comment: 14 pages, revised version to appear in the Proceedings of the QI2013
(Quantum Interactions) conferenc
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