Comments about the "News" article in Nature: Quantum 'spookiness' passes toughest test yet

Following is a discussion about this article in Nature Vol 525 27 August 2015, by B Hensen e.a].
To read this article select:"> For the "News and View" article about the same subject read: nature 29 Oct 2015 page 649.htm In the last paragraph I explain my own opinion.


It’s a bad day both for Albert Einstein and for hackers. The most rigorous test of quantum theory ever carried out has confirmed that the ‘spooky action at a distance’ that the German physicist famously hated — in which manipulating one object instantaneously seems to affect another, far away one — is an inherent part of the quantum world.
If you can trully demonstrate that you can instantaneously change the state of an object as predicted than you have performed an incredible act.

Einstein’s annoyance

In quantum mechanics, objects can be in multiple states simultaneously: for example, an atom can be in two places, or spin in opposite directions, at once. Measuring an object forces it to snap into a well-defined state. Furthermore, the properties of different objects can become ‘entangled’, meaning that their states are linked: when a property of one such object is measured, the properties of all its entangled twins become set, too.
The question is if this last sentence is true.
The issue is that separated particles are entangled. That means that certain particles are correlated. This is established by performing experiments on both particles to measure for example its spin. The result of such measurement will be that always when the spin of one particle is up the spin of the other particle is down.
The true issue is, if this property was already available before the measurement. I doubt that.
See also Reflection 1 - entanglement
He (Einstein) proposed that quantum particles do have set properties before they are measured, called hidden variables. And even though those variables cannot be accessed, he suggested that they pre-program entangled particles to behave in correlated ways.
The whole problem is in the details of the reactions that generated the two correlated particles.
In the 1960s, Irish physicist John Bell proposed a test that could discriminate between Einstein’s hidden variables and the spooky interpretation of quantum mechanics. He calculated that hidden variables can explain correlations only up to some maximum limit. If that level is exceeded, then Einstein’s model must be wrong.
It is also possible that Bell's calculation is wrong.

Entanglement swapping

In the latest paper3, which was submitted to the arXiv preprint repository on 24 August and has not yet been peer reviewed, a team led by Ronald Hanson of Delft University of Technology reports the first Bell experiment that closes both the detection and the communication loopholes. The team used a cunning technique called entanglement swapping to combine the benefits of using both light and matter. The researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 kilometres apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location. There, the two photons were entangled with each other — and this caused both their partner electrons to become entangled, too.
The interesting part are in the details of the last sentence.
From a conceptual point of view this experiment looks as follows: The question ofcourse is how can this be established.
In the experiment in Delft A1 and B1 are electrons.

Reflection 1 - entanglement

The concept of entanglement is partly based on the idea that measuring the entangled parameter of one object, instantaneous, that same parameter on the entangled object is set, as if that condition did not exist before the measurement.
This is completely different from the idea that entanglement happens at the moment when the two particles are created. That causes physical no problems.

Reflection 2 - Measurement

Reflection 3 - Loopholes

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Created: 19 February 2018

For further reading: The Quantum Theory and Reality Critical evaluation of the Scientific American Article by Bernard d'Espagnat.
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