Emilio Santos

Bell's theorem and the experiments: Increasing empirical support for local realism?

Abstract It is argued that local realism is a fundamental principle, which should be rejected only if experiments clearly show that it is untenable. A critical review is presented of the derivations of Bells inequalities and the experiments so far performed, with the conclusion that no valid, loophole-free, test exists of local realism, as against quantum mechanics. It is pointed out that, without any essential modification, quantum mechanics could be compatible with local realism. This suggests that the principle may be respected by nature.

Unreliability of performed tests of Bell's inequality using parametric down-converted photons

Abstract A local hidden variables model with a few adjustable parameters is presented which agrees with the results of every experiment performed using parametric down-converted photons for the test of a Bell inequality. This proves that local theories have not been refuted by these experiments. Improvements needed to make a reliable test are discussed.

Stochastic optics: a reaffirmation of the wave nature of light

Quantum optics does not give a local explanation of the coincidence counts in spatially separated photodetectors. This is the case for a wide variety of phenomena, including the anticorrelated counting rates in the two channels of a beam splitter, the coincident counting rates of the two “photons” in an atomic cascade, and the “antibunching” observed in resonance fluorescence.We propose a local realist theory that explains all of these data in a consistent manner. The theory uses a completely classical description of the electromagnetic field, but with boundary conditions of the far field that are equivalent to assuming a real fluctuating, zero-point field. It is related to stochastic electrodynamics similarly to the way classical optics is related to classical electromagnetic theory.The quantitative aspects of the theory are developed sufficiently to show that there is agreement with all experiments performed till now.

The Bell inequalities as tests of classical logic

Abstract A state (probability measure in the lattice of propositions) of a physical system allows defining a distance between any two propositions if the lattice is boolean (distributive). The triangle inequalities of the distances lead to the Bell inequalities provided a suitable definition of locality is introduced.

Neutron stars in generalized f(R) gravity

A gravity theory is considered with the Einstein-Hilbert Lagrangean R+aR2+bRμνRμν, Rμν being Ricci’s tensor and R the curvature scalar. The parameters a and b are taken of order 1 km2. Arguments are given which suggest that the effective theory so obtained might be a fair approximation of a viable theory. A numerical integration is performed of the field equations for a free neutron gas. The result is that the star mass increases with increasing central density until about 1 solar mass and then decreases. The baryon number increases monotonically, which suggests that the theory allows stars in equilibrium with arbitrary baryon number, no matter how large.

Quantum vacuum effects as generalized f(R) gravity: Application to stars

It is assumed that, for weak space-time curvature, the main gravitational effect of the quantum vacuum stress energy corresponds to adding two terms to the Einstein-Hilbert action, proportional to the square of the curvature scalar and to the contraction of two Ricci tensors, respectively. It is shown that compatibility with terrestrial and Solar System observations implies that the square roots of the coefficients of these terms should be either a few millimeters or a few hundred meters. It is shown that the vacuum contribution increase the stability of massive white dwarfs.

Hidden variables in quantum logic approach reexamined

Various impossibility proofs for hidden variables theories produced within the quantum logic approach are analyzed. A very general form of n‐term Bell‐type inequalities is given. From these inequalities a new impossibly proof for hidden variables theories able to reproduce all numerical results of quantum mechanics follows.

Type II parametric downconversion in the Wigner-function formalism: entanglement and Bell’s inequalities

We continue the analysis of our previous papers that were devoted to type I parametric downconversion, the extension to type II being straightforward. We show that entanglement, in the Wigner representation, is merely a correlation that involves both signals and vacuum fluctuations. An analysis of the detection process opens the way to a complete description of parametric downconversion in terms of pure Maxwell electromagnetic waves.

Local realist model for the coincidence rates in atomic-cascade experiments

Abstract We assume that the two photons emerging from an atomic cascade process are classical wave-packets with well defined intensities and states of elliptical polarization. Such weak light signals, when interacting with optical devices such as linear polarizers and quarter-wave plates, are assumed to undergo stochastic changes of intensity in addition to the change in polarization experienced by macroscopic signals. We show how such assumptions can lead, in a natural way, to an enhancement in the detection probability of certain signals, and hence to a family of models which fit the observed counting rates in all atomic-cascade experiments so far performed, including those which investigate the circular polarizations of the photons.

Parametric Down-Conversion Experiments in the Wigner Representation

The Wigner representation is developed in the Heisenberg picture for the study of experiments involving photon pairs created in the process of parametric down conversion. After the general description of a light beam and the theory of detection (restricted here to single count probabilities in the Wigner formalism) the theory of parametric downconversion is developed to the point of calculating the autocorrelations of the signal and idler beams. Two recent experiments are analyzed in detail: frustrated two-photon creation by interference, and induced coherence and indistinguishability.