In this text the ancient philosophical question of determinism (“Does every event have a cause ?”) will be re-examined. In the philosophy of science and physics communities the orthodox position states that the physical world is indeterministic: quantum events would have no causes but happen by irreducible chance. Arguably the clearest theorem that leads to this conclusion is Bell’s theorem. The commonly accepted ‘solution’ to the theorem is ‘indeterminism’, in agreement with the Copenhagen interpretation. Here it is recalled that indeterminism (...) is not really a physical but rather a philosophical hypothesis, and that it has counterintuitive and far-reaching implications. At the same time another solution to Bell’s theorem exists, often termed ‘superdeterminism’ or ‘total determinism’. Superdeterminism appears to be a philosophical position that is centuries and probably millennia old: it is for instance Spinoza’s determinism. If Bell’s theorem has both indeterministic and deterministic solutions, choosing between determinism and indeterminism is a philosophical question, not a matter of physical experimentation, as is widely believed. If it is impossible to use physics for deciding between both positions, it is legitimate to ask which philosophical theories are of help. Here it is argued that probability theory – more precisely the interpretation of probability – is instrumental for advancing the debate. It appears that the hypothesis of determinism allows to answer a series of precise questions from probability theory, while indeterminism remains silent for these questions. From this point of view determinism appears to be the more reasonable assumption, after all. (shrink)

In the May 15, 1935 issue of Physical Review Albert Einstein co-authored a paper with his two postdoctoral research associates at the Institute for Advanced Study, Boris Podolsky and Nathan Rosen. The article was entitled “Can Quantum Mechanical Description of Physical Reality Be Considered Complete?” (Einstein et al. 1935). Generally referred to as “EPR”, this paper quickly became a centerpiece in the debate over the interpretation of the quantum theory, a debate that continues today. The paper features a striking case (...) where two quantum systems interact in such a way as to link both their spatial coordinates in a certain direction and also their linear momenta (in the same direction). As a result of this “entanglement”, determining either position or momentum for one system would fix (respectively) the position or the momentum of the other. EPR use this case to argue that one cannot maintain both an intuitive condition of local action and the completeness of the quantum description by means of the wave function. This entry describes the argument of that 1935 paper, considers several different versions and reactions, and explores the ongoing significance of the issues they raise. (shrink)

Realist interpretations of quantum mechanics presuppose the existence of elements of reality that are independent of the actions used to reveal them. Such a view is challenged by several no-go theorems that show quantum correlations cannot be explained by non-contextual ontological models, where physical properties are assumed to exist prior to and independently of the act of measurement. However, all such contextuality proofs assume a traditional notion of causal structure, where causal influence flows from past to future according to ordinary (...) dynamical laws. This leaves open the question of whether the apparent contextuality of quantum mechanics is simply the signature of some exotic causal structure, where the future might affect the past or distant systems might get correlated due to non-local constraints. Here we show that quantum predictions require a deeper form of contextuality: even allowing for arbitrary causal structure, no model can explain quantum correlations from non-contextual ontological properties of the world, be they initial states, dynamical laws, or global constraints. (shrink)

Relying on some auxiliary assumptions, usually considered mild, Bell’s theorem proves that no local theory can reproduce all the predictions of quantum mechanics. In this work, we introduce a fully local, superdeterministic model that by explicitly violating ‘settings independence’—one of these auxiliary assumptions, requiring statistical independence between measurement settings and systems to be measured—is able to reproduce all the predictions of quantum mechanics. Moreover, we show that contrary to widespread expectations, our model can break settings independence without an initial state (...) that is too complex to handle, without visibly losing all explanatory power, and without outright nullifying all of experimental science. Still, we argue that our model is unnecessarily complicated and does not offer true advantages over its non-local competitors. We conclude that while our model does not appear to be a viable contender to its non-local counterparts, it provides the ideal framework to advance the debate over violations of statistical independence via the superdeterministic route. (shrink)

I describe a new framework for the articulation and analysis of Bell's theorems for arbitrarily complicated discrete physical scenarios. The framework allows for efficient proof of some new results, as well as generalizations of some older results already known for simpler cases. The generalized known results are: satisfaction of all Bell inequalities is equivalent to the existence of a joint probability function for all possible measurement contexts and stochastic versions of Bell's theorem are not stronger than deterministic versions. The new (...) results are: the straightforward generalization of parameter independence is inadequate when there are more than two observers, parameter independence is a necessary condition for observable probabilities to satisfy the Bell inequalities, and if the primary states can appear in isolation, and the observable probabilities satisfy all Bell inequalities, then parameter independence is a necessary condition for the primary states, too. (shrink)

From classical mechanics to quantum field theory, the physical facts at one point in space are held to be independent of those at other points in space. I propose that we can usefully challenge this orthodoxy in order to explain otherwise puzzling correlations at both cosmological and microscopic scales.

A physical mechanical sequence is proposed representing measurement interactions ‘hidden' within QM's proverbial ‘black box'. Our ‘beam splitter' pairs share a polar angle, but head in opposite directions, so ‘led' by opposite hemisphere rotations. For orbital ‘ellipticity', we use the inverse value momentum ‘pairs' of Maxwell's ‘linear' and ‘curl' momenta, seen as vectors on the Poincare spherical surface. Values change inversely from 0 to 1 over 90 degrees, then ± inverts.. Detector polarising screens consist of electrons with the same vector (...) distributions, but polar angles set independently by A & B. The absorption/re-emission interaction process is modelled as surface vector additions at the angle of polar latitude of each interaction. This ‘collapse' of characteristic ‘wave values' is really then simply ‘re-polarisation', with new ellipticity. We then obtain the relation Cosθ at polarisers. We may simplify this to new ellipses with major/minor axis values. Considering as spherical orbital angular momentum rotation we invoke the unique quality of spheres to rotate concurrently on three axes! Rotating on y or z axes concurrent with x axis spin can return surface points to starting positions with non-integer x axis rotations, from half to infinity!. Second interactions at photomultiplier/ analysers are identical but at two orthogonal ‘channels'. Vector addition interactions at BOTH channel orientations normally produce a vector value of adequate amplitude to give a *click* from the MAJOR axis direction. At the ‘crossover' points at near circular polarity the orthogonal ‘certainty' is ~ 50:50, so both or neither channels may produce a ‘click'. The apparently unphysical but proved ‘Malus' law' relation; Cos2θ emerges physically from the 2nd set of interactions. The main departure from QM's assumptions are; That the original pair members each actually possessed two inverse momenta sets; ‘curl' and ‘linear'. Also that complex ‘vector additions' of those pairs occurs. Vector quantities allow A & B to reverse their OWN finding by reversing dial setting, reproducing experimental outputs without problematic ‘non-locality'. (shrink)

A well known logical loophole for Bell’s theorem is that it relies on setting independence: the assumption that the state of a system is independent of the settings of a measurement apparatus probing the system. In this paper the implications of rejecting this assumption are studied from an operationalist perspective. To this end a generalization of the ontic models framework is proposed that allows setting dependence. It is shown that within this framework Bell’s theorem reduces to the conclusion that no-signaling (...) requires randomness at the epistemic level even if the underlying ontology is taken to be deterministic. The ideas underlying the framework are further used to defend setting dependence against the charges of being incompatible with free will and scientific methodology. The paper ends however with the sketch of a new problem for setting dependence: a necessary gap between the ontic and the epistemic level that may prevent the formulation of a successful setting dependent theory. (shrink)