We show that a method exists for deducing from Einstein locality all the possible inequalities for linear combinations of correlation functions. This allows us to show also that there is a complete observational equivalence of deterministic local theories and probabilistic local theories.

The Clauser–Horne approach used to derive experimentally measurable quantities for performing experiments on EPR paradox based on Type-I Spontaneous Parametric Down Conversion (SPDC) sources is discussed. It is proved that in this case the deduced Bell's type inequality does not correctly express separability and causality. A deeper analysis of the problem shows that the Clauser–Horne hypothesis of factorizability of joint detection probability cannot be considered so general as to describe this physical situation.

A Michelson interferometer with a phase-conjugate mirror (PCM) is described and discussed. The behavior of phase conjugate mirrors is discussed and the result of an experiment with a Michelson interferometer with a phase-conjugate mirror is described and commented. This interferometer has been proposed to be used to test the intrinsic non-locality of quantum mechanics. In this paper a new experimental setup to study the one-way velocity of light is proposed, which uses this new interesting device.

By following the analysis of De Caro and Garuccio [Phys. Rev. A 54, 174 (1996)], we show that the factorable state vector produced with a beam-splitter set on the paths of parametric down-converted photons violates some new inequalities that we deduce from local realism. These inequalities are more stringent than those used up to now in the discussion of such phenomena.

Probabilistic local realism for two correlated systems as formulated by Clauser and Horne in 1974 is shown to be necessarily based on a perfect specification of the state and on an individual definition of probability. All known realistic formulations of probability calculus are instead defined in terms of relative frequencies, and perfect specifications of states are impossible. We reformulate probabilistic local realism by using the relative frequency definition only and show that the Einstein, Podolsky, and Rosen paradox still obtains.

Mandel and Pfleegor have shown the existence of interference effects produced by the superposition of two independent single-mode lasers even under conditions in which one photon is absorbed before the next is emitted by one or the other source. We propose here a modification of their experiment which would establish (if the interferences persist) the simultaneous existence of waves and particles (photons), a result which is assumed as basis by the stochastic interpretation of quantum mechanics.

If the energy-absorbing radio-frequency spin-flipping device used in perfect crystal neutron interferometry is an intermediate measuring device, then the experimental results contradict the associated wave packet collapse and support the real existence of the de Broglie pilot waves in both arms while the neutron travels in only one.