Is the possible Bell's test loophole of entangled particles communicating at a non instantaneous but FTL speed addressed and eliminated?

Question

TLDR:

1. There seems to be a loophole in Bell's test that is not addressed or eliminated before we can successfully conclude that it proves that the Universe is unreal and non local. The entangled particles can still communicate at a non instantaneous but FTL speed. I'm unable to find any reference for such a loophole on the intenret. Is this loophole acknowledged and eliminated?

2. What happens if we perform the Modified Bell Test by Electromagnetic Isolation (MoBeTEIs) experiment mentioned below? What are the consequences of two different outcomes?

Please answer the above two questions pointwise separately to be more clear and avoid confusion. The rest of the post is about me explaining the background and why I think the question is valid.

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This is in the light of recent Nobel prize given to physicists

for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science

The claim is that they have conclusively proven that the result of Bell's test and the resulting violation of Bell inequalities confrims that the Universe is not locally real, by closing all the plausible loopholes except superdeterminism, which in general, is

fundamentally untestable, as the correlations can be postulated to exist since the Big Bang, making the loophole impossible to eliminate.

Another important loophole was the locality loophole where there was a possibility for the entangled particles to communicate at the speed of light. This was eliminated by using long distances between measurements of entangled particles, where both the measurements were made within the narrow timeframe shorter than the time required by light to travel between the two places.

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But, there seems to be another loophole which I'm not able to find being accounted for or being discussed.

There is still a possibility of non instantaneous but faster than light(FTL) signalling between the entangled particles.

FTL travel is not completely unproven, We already know Einstein's theory of relativity is at odds with quantum mechanics and his general theory of relativity is incomplete as it melts down at singularity in blackholes and at the beginning of the Universe.

Given this, it seems rather interesting that important features of quantum mechanics - non locality and unrealism, is proven assuming that the thoery of relativity is absolutely true, when we know that the latter is incomplete and is in odds with the very thing it is being used to prove.

The possibility of non-instantaneous but FTL signalling seems far more tenable and intutive rather than Universe being non-local and unreal. And therefore this seems to be a loophole for Bell's test.

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This loophole may be non falsifiable if the signalling is too weak a force to detect. But it is possible to block the signalling given that the entangled particles are using a force which is susceptible to shielding.

There are four known forces of nature:

Image Credit

The strong and weak nuclear forces can be excluded as it is short range acting.

Gravitational influence or force, as of now, cannot be shielded and gravitational shielding is still a hypothetical concept. So if the entangled particles are using gravitational force to interact, then as of now it is impossible to test it.

But given that electrons are charged particles and photons are electromagnetic in nature, it is more probable that if at all the entangled electrons and photons interact they possibly interact using electromagnetic interaction which can be shielded using electromagnetic shielding and lead shielding.

Regarding electromagnetic force travelling only at speed of light, it is still thoeretically possible for electromagnetic force to travel FTL, if the space between entangled particles itself is stretched and snaps when the measurement is made just like the diameter of the Universe(46.1 billion light years) is larger than the age of the Universe(13.8 billion years) and like shock wave in air moving at faster speed than sound.

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Modified Bell Test by Electromagnetic Isolation(MoBeTEIs) Experimental Setup:

This modified Bell test would have one extra feature of isolating measurement devices within a globe which can shield from electromagnetic force.

Initially entangled particles are created and sent to two measuring devices which are kept inside electromagnetic shielding globes with gates open, so as to let the electrons get inside.

Once the entangled particle enters the globe, before it is measured, the gates of the globe needs to be closed so as to not either let out or let in any electromagnetic signals.

There are two possible outcomes for this experiment and I think the following are the ramifications of the respective outcomes of the experiment.

1. Bell equality is still violated in MoBeTEIs, which maintains status quo assumption but we also know that entangled particles used in MoBeTEIs does not communicate using electromagnetic signals.

2. Bell equality is not violated in MoBeTEIs, proves the Universe to be local and real and also favours hidden variable theories. There will be huge ramifications to Copenhagen and Many worlds interpretation. The possibility FTL signalling will be confirmed.

What do you think happens if we actually perform the MoBeTEIs experiment? What would the different results mean according to you?

Answer 1

The word "loophole" is often thrown around in an imprecise way when it comes to Bell Experiments, but no matter how you define the term, any faster-than-light influence is not a "loophole".

Bell's argument is a proof by contradiction. The argument begins by assuming two things: (1) there is no faster than light influence, and (2) the future settings are uncorrelated with any past hidden variables relevant to the eventual outcomes. Given those assumptions, it proves an inequality, which is violated by experiment. Therefore at least one of the assumptions (1) or (2) must be wrong. That's the conclusion.

Positing that "maybe there are faster than light influences" is not a loophole, it's simply one of the possible conclusions of the above argument. Any such argument would be in agreement that (1) is false, which is the standard conclusion of Bell's argument, not anything new.

A true "loophole" is something that would allow both (1) and (2) to be true, despite Bell's Theorem and the experiments. For example, the detection efficiency loophole (now closed) used to be able to argue that (1) and (2) might still both be true.

Answer 2

There seems to be a loophole in Bell's test that is not addressed or eliminated before we can successfully conclude that it proves that the Universe is unreal and non local.

It doesn't prove the universe is non-realist or non-local. There is another interpretation of quantum mechanics consistent with Bell's test, that is local, realist, and deterministic: the Everett Interpretation, also known as the Many Worlds Interpretation.

'Realism' isn't about saying "the universe is unreal". Realism is about whether the wavefunction is real. Does the wavefunction constitute the actual true state of reality in between measurements, or is it just mathematics? The wavefunction seems to describe alternative things that could happen, but don't - what philosophers call counterfactuals.

We stare at our opponent across the poker table and wonder if he is holding the ace of spades in his hand. In our head, there is a probability distribution describing different branches, in some of which he does, and in others he doesn't, but only one of them will turn out to be real - to have a mind-independent existence. Our probability calculations work, but the alternative scenarios they are describing aren't real, they only exist in our minds.

Quantum mechanics seems to be saying that these alternative possibilities are real. The alternative paths interfere with one another. Does the wavefunction have a mind-independent existence, even when it is not being observed? Do complementary properties like position and momentum exist, before they are observed? The idea that these are real and meaningful, and not just imaginary artefacts of the mathematics, is called Realism.

But this seemingly runs headlong into the obvious fact that we see only one outcome. Where do all the others go?

One way out of the problem is to retreat to what we can see - to say that the only reality is what is observed, that reality jumps from one observation to the next, with nothing in between, and the observations follow statistical patterns as if there were these interfering wavefunctions in between them, but they shouldn't be taken seriously as a description of reality. Statements about things we cannot observe are scientifically meaningless. We simply don't know, and possibly never will.

This point of view is sometimes called the "Shut up and calculate" school. As Einstein put it to a colleague who followed this school: "Do you really believe that the moon isn't there when nobody looks?"

Another approach is to say the wavefunction is real, but collapses to a definite value when observed. This is the mainstream Copenhagen Interpretation, and what Bell assumed.

A third approach is to say the wavefunction is real and doesn't collapse. What happens is that the observer is a wavefunction too, and when the observer interacts with the particle, their wavefunctions become correlated. A particle in a superposition of possible outcomes results in an observer in a superposition of observers observing all those possible outcomes. The components of a linear superposition do not interact with one another (just as the superposed components of an electron's wavefunction do not repel one another), which is why we seem to see only one outcome. And because all the alternative outcomes are still around, the correlations can be explained when widely-separated entangled observers meet up to compare notes.

This third approach is thus consistent with the outcome of Bell's test, and is local, realist, and deterministic. It does, on the other hand imply the existence of a possibly-infinite number of unobservable entities!

The entangled particles can still communicate at a non instantaneous but FTL speed.

This doesn't work because in Special Relativity, 'instantaneous' depends on your reference frame. When two events A and B are simultaneous according to one observer, another observer moving past him in one direction will see A happen before B, and a different observer moving in the opposite direction will see B happen before A.

So for any pair of spacelike-separated events, there is some reference frame in which they are simultaneous, and some reference frame where the effect occurs before its cause.

Any effect that propagates faster than light will, to some relatively-moving observers, also propagate backwards in time.

This is a necessary consequence if the wavefunction collapses - the propagating collapse is a genuine change of the actual state of the universe, by realism, and will propagate backwards in time according to some observers, by relativity. Because there is an alternative interpretation of the observations that is local, we can be certain that there is no way to use this to communicate faster than light. All the parts that propagate faster than light are unobservable. It is the counterfactuals - the alternative outcomes that didn't happen - magically vanishing! According to some observers, they vanish even before the observation that made them vanish actually happens!!

But since this is an argument about matters that can never be experimentally tested, it's not science. It is philosophy, or metaphysics, or aesthetics. You can only pick an interpretation based on criteria like which is simpler, more elegant, more 'explanatory', more intuitively acceptable, or easier to calculate with.