4,624 research outputs found
Bell Inequalities for Position Measurements
Bell inequalities for position measurements are derived using the bits of the
binary expansion of position-measurement results. Violations of these
inequalities are obtained from the output state of the Non-degenerate Optical
Parametric Amplifier.Comment: revtex4, 2 figure
Convergence & Competition: United Ways and Community Foundations - A National Inquiry
This U.S. report summarizes key findings of the research that was commissioned to support the active dialogue among leaders of United Ways and other community foundations about their respective roles in community philanthropy and what the options for strategic co-existence -- if not full-fledged cooperation -- will look like in the coming years
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Why do the maximum intensities in modeled tropical cyclones vary under the same environmental conditions?
In this study w e explored why the different initial tropical cyclone structures can result in different steady‐state maximum intensities in model simulations with the same environmental conditions. We discovered a linear relationsh ip between the radius of maximum wind (rm) and the absolute angular momentum that passes through rm (Mm) in the model simulated steady‐state tropical cyclones that rm = aMm+b. This nonnegligible intercept b is found to be the key to making a steady‐state storm with a larger Mm more intense. The sensitivity experiments show that this nonzero b results mainly from horizontal turbulent mixing and decreases with decreased horizontal mixing. Using this linear relationship from the simulations, it is also found that the degree of supergradient wind is a function of Mm as well as the turbulent mixing length such that both a larger Mm and/or a reduced turbulent mixing length result in larger supergradient winds
How quantum correlations enhance prediction of complementary measurements
If there are correlations between two qubits then the results of the
measurement on one of them can help to predict measurement results on the other
one. It is an interesting question what can be predicted about the results of
two complementary projective measurements on the first qubit. To quantify these
predictions the complementary \emph{knowledge excesses} are used. A non-trivial
constraint restricting them is derived. For any mixed state and for arbitrary
measurements the knowledge excesses are bounded by a factor depending only on
the maximal violation of Bell's inequalities. This result is experimentally
verified on two-photon Werner states prepared by means of spontaneous
parametric down-conversion.Comment: 4 pages, 4 figure
Energy-time entanglement, Elements of Reality, and Local Realism
The Franson interferometer, proposed in 1989 [J. D. Franson, Phys. Rev. Lett.
62:2205-2208 (1989)], beautifully shows the counter-intuitive nature of light.
The quantum description predicts sinusoidal interference for specific outcomes
of the experiment, and these predictions can be verified in experiment. In the
spirit of Einstein, Podolsky, and Rosen it is possible to ask if the
quantum-mechanical description (of this setup) can be considered complete. This
question will be answered in detail in this paper, by delineating the quite
complicated relation between energy-time entanglement experiments and
Einstein-Podolsky-Rosen (EPR) elements of reality. The mentioned sinusoidal
interference pattern is the same as that giving a violation in the usual Bell
experiment. Even so, depending on the precise requirements made on the local
realist model, this can imply a) no violation, b) smaller violation than usual,
or c) full violation of the appropriate statistical bound. Alternatives include
a) using only the measurement outcomes as EPR elements of reality, b) using the
emission time as EPR element of reality, c) using path realism, or d) using a
modified setup. This paper discusses the nature of these alternatives and how
to choose between them. The subtleties of this discussion needs to be taken
into account when designing and setting up experiments intended to test local
realism. Furthermore, these considerations are also important for quantum
communication, for example in Bell-inequality-based quantum cryptography,
especially when aiming for device independence.Comment: 18 pages, 7 figures, v2 rewritten and extende
Modeling the Singlet State with Local Variables
A local-variable model yielding the statistics from the singlet state is
presented for the case of inefficient detectors and/or lowered visibility. It
has independent errors and the highest efficiency at perfect visibility is
77.80%, while the highest visibility at perfect detector-efficiency is 63.66%.
Thus, the model cannot be refuted by measurements made to date.Comment: 15 pages, 13 figure
Covariant Helicity-Coupling Amplitudes: A New Formulation
We have worked out covariant amplitudes for any two-body decay of a resonance
with an arbitrary non-zero mass, which involves arbitrary integer spins in the
initial and the final states. One key new ingredient for this work is the
application of the total intrinsic spin operator which is given
directly in terms of the generators of the Poincar\'e group.
Using the results of this study, we show how to explore the Lorentz factors
which appear naturally, if the momentum-space wave functions are used to form
the covariant decay amplitudes. We have devised a method of constructing our
covariant decay amplitudes, such that they lead to the Zemach amplitudes when
the Lorentz factors are set one
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
Ranking the harm of non-medically used prescription opioids in the UK
A panel of nine experts applied multi-criteria decision analysis (MCDA) to determine the relative overall harm to users and harms to others of street heroin (injected and smoked) and eleven non-medically used prescription opioids. The experts assessed harm scores for each of the 13 opioids on each of 20 harm criteria, weighted the criteria and explored the resulting weighted harm scores for each opioid. Both forms of heroin scored very high: overall harm score of 99 for injected heroin and 72 for smoked heroin on a scale of 0–100. The main feature that distinguishes both forms of street heroin use is that their harm to others is more than five times that of the other eleven opioids. The overall harm score of fentanyl (including injection of fentanyl extracted from patches) and diamorphine (medically prescribed form of heroin) was 54 and 51, respectively, whereas that of orally used opioids ranged from 32 (pethidine) to 11 (codeine-containing pharmaceuticals). Injected street heroin, fentanyl and diamorphine emerged as most harmful to users, with the latter two very low in harm to others. Pethidine, methadone, morphine and oxycodone are also low in harm to others, while moderate in harm to users. We conclude that the overall harms of non-medically used prescription opioids are less than half that of injected street heroin. These data may give a basis for precautionary regulatory measures that should be considered if the rising trend in non-medical use of prescription opioids were to become evident in the UK
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