# News

23/09/2018

## Quantum Trajectories: Real or Surreal?

The claim of Kocsis et al. to have experimentally determined “photon trajectories” calls for a re-examination of the meaning of “quantum trajectories”. We will review the arguments that have been assumed to have established that a trajectory has no meaning in the context of quantum mechanics. We show that the conclusion that the Bohm trajectories should be called “surreal” because they are at “variance with the actual observed track” of a particle is wrong as it is based on a false argument. We also present the results of a numerical investigation of a double Stern-Gerlach experiment which shows clearly the role of the spin within the Bohm formalism and discuss situations where the appearance of the quantum potential is open to direct experimental exploration.

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**By Basil J. Hiley and Peter Van Reeth***This abstract belongs to an article of the Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"*Visit EmQM17 symposium page

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22/09/2018

## Feynman Paths and Weak Values

There has been a recent revival of interest in the notion of a ‘trajectory’ of a quantum particle. In this paper, we detail the relationship between Dirac’s ideas, Feynman paths and the Bohm approach. The key to the relationship is the weak value of the momentum which Feynman calls a transition probability amplitude. With this identification we are able to conclude that a Bohm ‘trajectory’ is the average of an ensemble of actual individual stochastic Feynman paths. This implies that they can be interpreted as the mean momentum flow of a set of individual quantum processes and not the path of an individual particle. This enables us to give a clearer account of the experimental two-slit results of Kocsis et al. View Full-Text / Download Paper

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**By Robert Flack and Basil J. Hiley***This abstract belongs to an article of the Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"*Visit EmQM17 symposium page

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21/09/2018

## Experimental Non-Violation of the Bell Inequality

A finite non-classical framework for qubit physics is described that challenges the conclusion that the Bell Inequality has been shown to have been violated experimentally, even approximately. This framework postulates the primacy of a fractal-like ‘invariant set’ geometry IU in cosmological state space, on which the universe evolves deterministically and causally, and from which space-time and the laws of physics in space-time are emergent. Consistent with the assumed primacy of IU , a non-Euclidean (and hence non-classical) metric gp is defined in cosmological state space. Here, p is a large but finite integer (whose inverse may reflect the weakness of gravity). Points that do not lie on IU are necessarily gp -distant from points that do. gp is related to the p-adic metric of number theory. Using number-theoretic properties of spherical triangles, the Clauser-Horne-Shimony-Holt (CHSH) inequality, whose violation would rule out local realism, is shown to be undefined in this framework. Moreover, the CHSH-like inequalities violated experimentally are shown to be gp -distant from the CHSH inequality. This result fails in the singular limit p=∞ , at which gp is Euclidean and the corresponding model classical. Although Invariant Set Theory is deterministic and locally causal, it is not conspiratorial and does not compromise experimenter free will. The relationship between Invariant Set Theory, Bohmian Theory, The Cellular Automaton Interpretation of Quantum Theory and p-adic Quantum Theory is discussed. View Full-Text / Download Paper

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**By T. N. Palmer***This abstract belongs to an article of the Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"*Visit EmQM17 symposium page

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20/09/2018

## The Montevideo Interpretation of Quantum Mechanics: A Short Review

The Montevideo interpretation of quantum mechanics, which consists of supplementing environmental decoherence with fundamental limitations in measurement stemming from gravity, has been described in several publications. However, some of them appeared before the full picture provided by the interpretation was developed. As such, it can be difficult to get a good understanding via the published literature. Here, we summarize it in a self-contained brief presentation including all its principal elements. View Full-Text / Download Paper

*This abstract belongs to an article of the Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"*

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**By Rodolfo Gambini and Jorge Pullin**Visit EmQM17 symposium page

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## Spooky Action at a Temporal Distance

Since the discovery of Bell’s theorem, the physics community has come to take seriously the possibility that the universe might contain physical processes which are spatially nonlocal, but there has been no such revolution with regard to the possibility of temporally nonlocal processes. In this article, we argue that the assumption of temporal locality is actively limiting progress in the field of quantum foundations. We investigate the origins of the assumption, arguing that it has arisen for historical and pragmatic reasons rather than good scientific ones, then explain why temporal locality is in tension with relativity and review some recent results which cast doubt on its validity. View Full-Text / Download Paper

*This abstract belongs to an article of the Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"*

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**By Emily Adlam**Visit EmQM17 symposium page

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## Observables and Unobservables in Quantum Mechanics: How the No-Hidden-Variables Theorems Support the Bohmian Particle Ontology

The paper argues that far from challenging—or even refuting—Bohm’s quantum theory, the no-hidden-variables theorems in fact support the Bohmian ontology for quantum mechanics. The reason is that (i) all measurements come down to position measurements; and (ii) Bohm’s theory provides a clear and coherent explanation of the measurement outcome statistics based on an ontology of particle positions, a law for their evolution and a probability measure linked with that law. What the no-hidden-variables theorems teach us is that (i) one cannot infer the properties that the physical systems possess from observables; and that (ii) measurements, being an interaction like other interactions, change the state of the measured system. View Full-Text / Download Paper

*This abstract belongs to an article of the Special Issue "Emergent Quantum Mechanics – David Bohm Centennial Perspectives"*

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**By Dustin Lazarovici, Andrea Oldofredi and Michael Esfeld**Visit EmQM17 symposium page

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