What is entanglement?

I conjecture that only those states of light whose Wigner function is positive are real states, and give arguments suggesting that this is not a serious restriction. Hence it follows that the Wigner formalism in quantum optics is capable of interpretation as a classical wave field with the addition of a zeropoint contribution. Thus entanglement between pairs of photons with a common origin occurs because the two light signals have amplitudes and phases, both below and above the zeropoint intensity level, which are correlated with each other.Comment: 17 pages, no figure

Mathematical and physical meaning of the Bell inequalities

It is shown that the Bell inequalities are closely related to the triangle inequalities involving distance functions amongst pairs of random variables with values $\left\{ 0,1\right\}$. A hidden variables model may be defined as a mapping between a set of quantum projection operators and a set of random variables. The model is noncontextual if there is a joint probability distribution. The Bell inequalities are necessary conditions for its existence. The inequalities are most relevant when measurements are performed at space-like separation, thus showing a conflict between quantum mechanics and local realism (Bell's theorem). The relations of the Bell inequalities with contextuality, Kochen-Specker theorem, and quantum entanglement are briefly discussed.Comment: Relevant new references added. Section of the physical meaning revise

Dark matter as an effect of the quantum vacuum

The interaction between the quantum vacuum and a weak gravitational field is calculated for the vacuum fields of quantum electrodynamics. The result shows that the vacuum state is modified by the gravitational field, giving rise to a nonzero interaction energy. This suggests a model that fits in the main properties of the hypothetical dark matter in galactic haloes.Comment: 26 pages. arXiv admin note: text overlap with arXiv:1702.03430 by other author

Vacuum fluctuations the clue for a realistic interpretation of quantum mechanics

Arguments are gived for the plausibility that quantum mechanics is a stochastic theory and that many quantum phenomena derive from the existence of a real noise consisting of vacuum fluctuations of all fundamental fields existing in nature. Planck's constant appears as the parameter fixing the scale of the fluctuations. Hints for an intuitive explanation are offered for some typical quantum features, like the uncertainty principle or the particle behaviour of fields. It is proposed that the recent discovery of dark energy in the universe is an argument for the reality of the vacuum fluctuations. A study is made of the compatibility of the model with the results of performed tests of Bell\'{}s inequalities.Comment: 34 pages. arXiv admin note: substantial text overlap with arXiv:1203.5688, arXiv:1205.091

Space-time curvature due to quantum vacuum fluctuations: An alternative to dark energy?

It is pointed out that quantum vacuum fluctuations may give rise to a curvature of space-time equivalent to the curvature currently attributed to dark energy. A simple calculation is made, which suggests that the value of the dark energy density is roughly given by the product of Newton constant time the quantity m^6 c^4 h^-4, m being a typical mass of elementary particles. The estimate is compatible with observations

Relation of the Bell inequalities with quantum logic, hidden variables and information theory

I review the relation of the Bell inequalities - characteristic of (classical) probabilities defined on Boolean logics - with noncontextual and local hidden variables theories of quantum mechanics and with quantum information.Comment: 12 page

Preliminary analysis of a recent experiment by F. A. Bovino

An analysis is made of the results of a recent polarization correlation experiment by Bovino (unpublished) where about 60,000 data have been obtained. I assume that the state of the photon pairs produced in the source (a non-linear crystal) are in a (slightly)non-maximally entangled state and the most relevant non-idealities of the set-up are taken into account. A comparison is made between the predictions of quantum mechanics and a simple family of local hidden varaibles models with the result that the former is violated by more than 4 standard deviations whislt the data are compatible with the family of local models.Comment: 10 pages, no figure

On possible memory effects in tests of Bell inequalities

It is shown that memory effects in experiments measuring correlations in entangled photon pairs are not able to produce a relevant loophole for the test of local hidden variables theories.Comment: Errors correcte

How photon detectors remove vacuum fluctuations

The main argument against the reality of the electromagnetic quantum vacuum fluctuations is that they do not activate photon detectors. In order to met this objection I propose a model of photocounting which, in the simple case of a light signal with constant intensity, predicts a counting rate proportional to the intensity, in agreement with the standard quantum result.Comment: 8 pages, no figures, corrected error in solution of differential equation, conclusions are essentially the sam

Metric fluctuations, solution to the superluminal neutrino problem?

It is shown that the measured neutrino velocity, apparently violating relativity theory, is compatible with (general) relativistic causality provided that we assume that the metric of spacetime fluctuates at short distances.Comment: 4 page