16,777 research outputs found
Probing multipartite entanglement in a coupled Jaynes-Cummings system
We show how to probe multipartite entanglement in coupled Jaynes-Cummings
cells where the degrees of freedom are the electronic energies of each of the
atoms in separate single-mode cavities plus the single-mode fields
themselves. Specifically we propose probing the combined system as though it is
a dielectric medium. The spectral properties and transition rates directly
reveal multipartite entanglement signatures. It is found that the Hilbert space
of the cell system can be confined to the totally symmetric subspace of two
states only that are maximally-entangled W states with 2N degrees of freedom
Entanglement vs. the quantum-to-classical transition
We analyze the quantum-to-classical transition (QCT) for coupled bipartite
quantum systems for which the position of one of the two subsystems is
continuously monitored. We obtain the surprising result that the QCT can emerge
concomitantly with the presence of highly entangled states in the bipartite
system. Furthermore the changing degree of entanglement is associated with the
back-action of the measurement on the system and is itself an indicator of the
QCT. Our analysis elucidates the role of entanglement in von Neumann's paradigm
of quantum measurements comprised of a system and a monitored measurement
apparatus
MEASUREMENT OF PRICE RISK IN REVENUE INSURANCE: IMPLICATIONS OF DISTRIBUTIONAL ASSUMPTIONS
A variety of crop revenue insurance programs have recently been introduced. A critical component of revenue insurance contracts is quantifying the risk associated with stochastic prices. Forward-looking, market-based measures of price risk which are often available in form of options premia are preferable. Because such measures are not available for every crop, some current revenue insurance programs alternatively utilize historical price data to construct measures of price risk. This study evaluates the distributional implications of alternative methods for estimating price risk and deriving insurance premium rates. A variety of specification tests are employed to evaluate distributional assumptions. Conditional heteroskedasticity models are used to determine the extent to which price distributions may be characterized by nonconstant variances. In addition, these models are used to identify variables which may be used for conditioning distributions for rating purposes. Discrete mixtures of normals provide flexible parametric specifications capable of recognizing the skewness and kurtosis present in commodity pricesRisk and Uncertainty,
On the epistemic view of quantum states
We investigate the strengths and limitations of the Spekkens toy model, which
is a local hidden variable model that replicates many important properties of
quantum dynamics. First, we present a set of five axioms that fully encapsulate
Spekkens' toy model. We then test whether these axioms can be extended to
capture more quantum phenomena, by allowing operations on epistemic as well as
ontic states. We discover that the resulting group of operations is isomorphic
to the projective extended Clifford Group for two qubits. This larger group of
operations results in a physically unreasonable model; consequently, we claim
that a relaxed definition of valid operations in Spekkens' toy model cannot
produce an equivalence with the Clifford Group for two qubits. However, the new
operations do serve as tests for correlation in a two toy bit model, analogous
to the well known Horodecki criterion for the separability of quantum states.Comment: 16 pages, 9 figure
The association between retinal vein ophthalmodynamometric force change and optic disc excavation
Aim: Retinal vein ophthalmodynamometric force (ODF) is predictive of future optic disc excavation in glaucoma, but it is not known if variation in ODF affects prognosis. We aimed to assess whether a change in ODF provides additional prognostic information. Methods: 135 eyes of 75 patients with glaucoma or being glaucoma suspects had intraocular pressure (IOP), visual fields, stereo optic disc photography and ODF measured on an initial visit and a subsequent visit at mean 82 (SD 7.3) months later. Corneal thickness and blood pressure were recorded on the latter visit. When venous pulsation was spontaneous, the ODF was recorded as 0 g. Change in ODF was calculated. Flicker stereochronoscopy was used to determine the occurrence of optic disc excavation, which was modelled against the measured variables using multiple mixed effects logistic regression. Results: Change in ODF (p=0.046) was associated with increased excavation. Average IOP (p=0.66) and other variables were not associated. Odds ratio for increased optic disc excavation of 1.045 per gram ODF change (95% CI 1.001 to 1.090) was calculated. Conclusion: Change in retinal vein ODF may provide additional information to assist with glaucoma prognostication and implies a significant relationship between venous change and glaucoma patho-physiology
Generalized W-Class State and its Monogamy Relation
We generalize the W class of states from qubits to qudits and prove
that their entanglement is fully characterized by their partial entanglements
even for the case of the mixture that consists of a W-class state and a product
state .Comment: 12 pages, 1 figur
Monogamy and polygamy for multi-qubit entanglement using R\'enyi entropy
Using R\'enyi- entropy to quantify bipartite entanglement, we prove
monogamy of entanglement in multi-qubit systems for . We also
conjecture a polygamy inequality of multi-qubit entanglement with strong
numerical evidence for with
.Comment: 19 pages, 2 figure
Classical Physics and Quantum Loops
The standard picture of the loop expansion associates a factor of h-bar with
each loop, suggesting that the tree diagrams are to be associated with
classical physics, while loop effects are quantum mechanical in nature. We
discuss examples wherein classical effects arise from loop contributions and
display the relationship between the classical terms and the long range effects
of massless particles.Comment: 15 pages, 3 figure
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