So, we (the observers) determine the realism?

@Vikash It is not always true that the observer deteremines the event.In some cases  you can have to have observer independent evolution of the quantum system but at the cost of losing LOCAL realism.That is the whole point of contextuality-locality correlations.

The statement is not self contradictory think of any lorentz transformation.The transformation between proper time and coordinate time can be done,but these two transformations cannnot be observed by the same observer.The transformation between two quantities does not imply simultaneous existence.

@Kralj If the observing system is a quantum system won't it then lead to 'Wavefunction of the universe' type arguments?

All the physicists did not understand what the observer is!

The observer means only interaction!

That is why nobody understood decoherence in Double slit experiment!

If you replace the detector with a piece of metal the wave will collapse into a particle because of my theory photon – graviton interaction, it is my theory!

@adrian have you come up with an S-matrix for the photon graviton interaction?

There is the object and the observer before the measurement. There is a changed object and changed observer after the measurement act. I would not say unequivocally that only the observer is the cause of measurement. After all, his intentions have meant some expectations about the object before. Perhaps it is due to the localization of non-locality, we have the opportunity to continuously expand our outlook exploring the reality.

https://en.wikipedia.org/wiki/Counterfactual_definiteness

For me nonlocality is not a manifestation of realism (or objectivity)

That is one reason that the results of QM seem so strange.

It is generally acknowledged that QM does not seem reasonable to normal intuition.

Also agree with Vasili. A measurement can be influenced by prior measurement, if very little time has gone by.

What about the results from classical mechanics? Are they objective?

I understand this as follows :

When non-locality and contextuality are tested at different times, the results give :

• Test non-locality (= check whether inequality for locality is violated) => one observes non-locality (intrication of photons)
• Test contextuality (= check whether inequality for non-contextuality is violated) => one observes contextuality (values for photons influenced by measurement conditions)

 In the article, they have tested both inequalities at the same time and discovered that :

• When non-locality is checked, contextuality cannot be observed (no influence of measurement conditions upon values) : the classical everyday world reigns with its non-contextuality
• When contextuality is checked, non-locality cannot be observed (no intrication of photons) : the classical everyday world reigns with its locality

They conclude that non-locality and contextuality are two faces of the same thing. And this is related to a realist interpretation of QM : the classical everyday world reigns outside the measurement.

In QM there is no prexisting reality without observation. In Classical Mechanics you can assume there is.

The discourse is reduced to possible answers and probabilities thereof.

>Juan,

This is indeed the Copenhagen interpretation (majority of researchers). And I agree with you : as long as QM is not fundamentally understood, just look at possible answers and probabilities thereof.

@ Ales

Two questions:  Is it safe to say that quantum mechanics is not resolved and lacks consensus among the scientific community?

Second, as per your say, if the observer disturbs (sees) the system, does the observer also gets disturbed (seen) by the system?

From paradoxes and contradictions, as a rule, going beyond the theory working area should be (or at least awareness about phenomena framework which theory can describe).

The observer disturbed by /measurement/ interaction. By the way, it is easier to understand if we consider the interaction between the two observers (instead of any object and the observer).

Yes, quantum mechanics (QM) has several counter-intuitive features. This is annoying for creativity since creativity rests significantly upon intuition. So Pandora boxes are opened on all kind of interpretation or denial (e.g. of a basic assumption of realism).

However even not really understood (see Feynman's "Nobody understands ...") QM works very well in practice. And common sense is not necessarily the right way towards discovery. As a result Pandora boxes are opened on "interpretation" or not (no basic assumption of realism) ....:=) 

Who knows ? Maybe there is something more fundamental to QM which reconciles observations with intuition and also explains why it works so well. Maybe one is right to suspect some kind of influence of the system on the observer. Maybe it has to make with quantum information .....?      

@Vikash,

There are basic misunderstandings here. You are totally confused. The statement,

"Since nonlocality and contextuality can be thought of as two different manifestations of the basic assumption of realism, then one of them can be transformed into the other, but both cannot exist at the same time because they are essentially the same thing."

is wrong.

1) QM disagrees with the realism, as Juan Weisz correctly pointed out. Realism says that before each single trial in the measurement, there exists some reality that determines the result of that trial. Note the word "determines". QM says that measurement results are non-deterministic.

2) Of course nonlocality and contextuality coexist. Nonlocality says that the result we get "here" depends on type and result of the measurement done "there", and "there' is very far, s.t. no classical type of influence takes place between the measurements. Contextuality says the same, but insists on the type of the measurement done "there", and less on the distance between measurement places.

You also say

"As the physicists explain, the reason for the nonlocality-contextuality tradeoff arises from the fact that both properties have the same root: the assumption of realism, which is the assumption that the physical world exists independent of our observations, and that the act of observation does not change it."

Who explained you? Which trade-off, where from did you take it? Physicists explain the opposite, i.e. QM does not admit the realism - see what I said above.

I also saw the question if the observed system influences the observer or its apparatus. The answer is two-fold. As long as the measurement is quantum, i.e. we entangle the observed system with other quantum system(s), they influence one another. The role of the macroscopic apparatus is that it "collapses" the measured wave-function on one of its component eigenfunctions, and reports the respective result. If that can be considered as influence of the observed system on the apparatus, is matter of taste.

@ Sofia,

The two quotations you are criticizing are taken from the report of the journalist who has interviewed the authors of following article (see the link in the question) :

Xiang Zhan, et al. "Realization of the Contextuality-Nonlocality Tradeoff with a Qubit-Qutrit Photon Pair." Physical Review Letters. DOI: 10.1103/PhysRevLett.116.090401

Reference to realism would have been done by Dr Xiang Zhan or a co-author.

As I have momentarily no direct access to "Physical Review Letters", could you give your opinion on the article (experiment) itself ?

Thanks

@ Sofia,

Here is the link to the abstract :

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.090401

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.090401