Comments about "Bell test experiments" in Wikipedia

This document contains comments about the article Bell test experiments in Wikipedia
In the last paragraph I explain my own opinion.




The article starts with the following sentence.

1. Overview

One feature of the theory of quantum mechanics under debate was the meaning of Heisenberg's uncertainty principle.
The Heisenberg's uncertainty principle is not a physical law. In some sense it is a reflection of our human capabilities to measure the physical reality.
The principle states that the determination of the particle's momentum makes an observation of its position impossible, and vice versa.
That is correct. But that does not mean that at any instant the particle does not have a momentum and position.
In 1935, Einstein, Boris Podolsky, and Nathan Rosen published a claim that quantum mechanics predicts that more information about a pair of entangled particles could be observed than Heisenberg's principle allowed, which would only be possible if information were travelling instantly between the two particles.
This sentence is very tricky because Heisenberg's principle is tricky.
IMO the issue is: How do you explain entanglement i.e. the fact that the same parameters (for example spin) of two particles or photons are correlated.
Furthermore, Einstein argued that the hidden variables should obey the condition of locality: Whatever the hidden variables actually are, the behavior of the hidden variables for one particle should not be able to instantly affect the behavior of those for another particle far away.
That is 100% correct. The origin of the entanglement lies in the reaction which created the particles.
In 1964, John Stewart Bell proposed his now famous theorem, which states that no physical theory of hidden local variables can ever reproduce all the predictions of quantum mechanics.
This sentence is too general and difficult to understand. Whet means: 'all the predictions of quantum mechanics'?
At least mention one prediction for which the 'theory of hidden local variables' has no explanation.
For example: The fact that particles can be entangled, is that a prediction of quantum mechanics?
If Yes: What is the physical explanation (using QM)?.
Implicit in the theorem is the proposition that the determinism of classical physics is fundamentally incapable of describing quantum mechanics.
It is rather silly to assume that the rules that describe elementary particles i.e the movement of the electrons in an atom are the same as for example how the earth moves around the Sun. Both phenomena are described by certain laws, which operates at complete different scales.
A typical experiment involves the observation of particles, often photons, in an apparatus designed to produce entangled pairs and allow for the measurement of some characteristic of each, such as their spin.
This sentence is wrong: A typical experiment involves the production of photon pairs and the observation of these particles, often photons, in an apparatus designed for the measurement of some characteristic of each, such as their spin.
The result can be that the photons are entangled.
The results of the experiment could then be compared to what was predicted by local realism and those predicted by quantum mechanics.
Some experiments will agree with local realism (throwing a dice at two places simultaneous) and some with quantum mechanics (Spontaneous parametric down-conversion)

2 Conduct of optical Bell test experiments

2.1 A typical CHSH (two-channel) experiment

2.2 A typical CH74 (single-channel) experiment

3 Experimental assumptions

4 Notable experiments

5. Loopholes

6. See also

Following is a list with "Comments in Wikipedia" about related subjects

Reflection 1 - Bell inequality

Reflection 2

Reflection 3


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Created: 21 May 2018

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