Can quantum entanglement be explained by holism?

Question

In quantum mechanics, during entanglement, two particles can have various correlations even when separated at a large distance. If one creates an entangled pair, sends each far away out to a measuring device, and if they are anti correlated with respect to spin, one observes either a (0,1) value or a (1,0) value.

In other words, if Bob observes that the particle is spin up, he now knows that Alice’s particle will be spin down. If he observes the particle is spin down, he now knows that Alice’s particle will be spin up.

Crucially, John Bell showed that these particles were not locally determined. To use an analogy, suppose if I have two boxes and I put a left glove and a right glove in each. If I open one of the boxes, and I see a left glove, I know that the other box has the right glove, even if these boxes were separated far away from each other. This is easily explained by the fact that one of the boxes “always” or was “locally determined” to have the right or the left glove depending on how I placed the gloves in each box.

John Bell showed using a theorem that this is not what’s happening. In a very real sense, neither box has the right or left glove in it before I open it. And yet somehow, when I open one box, even though in a real sense a box has a 50/50 chance of either being the right or left, once I open it, and it’s left, the other box is guaranteed to be the right. It is as if the probabilities “collapse” after measurement.

Naturally, Bell himself thought that this implied that the measurement of one particle somehow influences the measurement of another particle. He eventually championed a deterministic theory called Bohmian Mechanics before his death. As he says,

Let me summarize once again the logic that leads to the impasse. The EPRB correlations are such that the result of the experiment on one side immediately foretells that on the other, whenever the analyzers happen to be parallel. If we do not accept the intervention on one side as a causal influence on the other, we seem obliged to admit that the results on both sides are determined in advance anyway, independently of the intervention on the other side, by signals from the source and by the local magnet setting. But this has implications for non-parallel settings which conflict with those of quantum mechanics. So we cannot dismiss intervention on one side as a causal influence on the other. (Bell 1981a, reprinted 1987c: 149)

The problem is that if there are influences between particles, they would be non local. In other words, it would involve influences that are faster than the speed of light.

Some have argued that the need to posit non local influences comes from misplaced intuitions. Because the particles are entangled, one must treat them as one, inseparable object (a sort of holism) even when separated at a large distance. As the SEP puts it,

In orthodox quantum mechanics as well as in any other current quantum theory that postulates non-locality (i.e., influences between distant, space-like separated systems), the influences between the distant measurement events in the EPR/B experiment do not propagate continuously in space-time. They seem to involve action at a distance. Yet, a common view has it that these influences are due to some type of holism and/or non-separability of states of composite systems, which are characteristic of systems in entangled states (like the spin singlet state), and which exclude the very possibility of action at a distance

Thus, some deny that there are causal influences between the particles, as described as such:

Finally, there are those who question the assumption that factorizability is a locality condition (Fine 1981, 1986, pp. 59-60, 1989b, Cartwright 1989, chaps. 3 and 6, Chang and Cartwright 1993). Accordingly, they deny that non-factorizability implies non-locality. The main thrust of this line of reasoning is that the principle of the common cause is not generally valid. Some, notably Cartwright (1989) and Chang and Cartwright (1993), challenge the assumption that common causes always screen off the correlation between their effects, and accordingly they question the idea that non-factorizability implies non-locality. Others, notably Fine, deny that correlations must have causal explanation.

At the same time,

While these arguments challenge the view that the quantum realm as depicted by non-factorizable models for the EPR/B experiment must involve non-locality, they do not show that viable local, non-factorizable models of the EPR/B experiment (i.e., viable models which do not postulate any non-locality) are possible. Indeed, so far none of the attempts to construct local, non-factorisable models for EPR/B experiments has been successful.

So how should one then think about this? Should one agree with John Bell that this does likely imply some sort of causal influences occurring between these particles? Or should one think that this is because of misplaced intuitions? Personally, simply stating that the particles should be treated as one, inseparable object and thus causal influences are not needed seems to just beg the question. The question being: how do the particles remain correlated even when separated when in a real sense each of their individual spins is not determined before measurement? It seems circular to then say that it’s because they should be treated as an inseparable object, which is just another way of saying that they remain correlated at large distances.

On the other hand, there has been no demonstration of superluminal influences although I’m not sure how that would be demonstrated anyways. Couldn’t one argue that the very experiments in question demonstrate it? There are theories that show that one cannot use this for signalling since from Alice’s perspective, the outcome is random, and thus she can’t force an outcome in advance to send to Bob. But this even if true would rule out signalling, not physical influences between the particles that we may or may not hijack for other purposes.

So I am at an impasse. Is this impasse resolvable?

P.S. I am aware of the many worlds interpretation that arguably seems to resolve this impasse neatly. It simply states that everything occurs which removes the vagueness of traditional QM without positing superluminal influences. My question is moreso about how one would resolve this impasse if there are no multiple realities

Answer 1

Entanglement and Bell correlations are a result of quantum theory. So if you want to work out if there is an explanation of Bell correlations you should work that out using quantum theory.

This gets us into the issue of working out what quantum theory implies about reality. There is a controversy about this that is said to be about the interpretation of quantum theory. These "interpretations" of quantum theory fall into three categories.

The first category asserts that there is no account of what is happening in reality and we should just use equations of quantum theory without such an account: the Copenhagen and statistical interpretations take this approach. One problem with this approach is that setting up an experiment correctly requires comparing what is going on in the experiment with the conditions you want to produce in the experiment to test a theory. If you have no account of what is happening in reality, then you have no account of what is happening in the experiment and so no way to say if it has been set up correctly. This approach to quantum theory would say there is no explanation of the correlations.

Some interpretations modify quantum theory. The spontaneous collapse interpretation claims that once in a while the wavefunction collapses at random:

https://arxiv.org/abs/2310.14969

Pilot wave theory modifies quantum theory by adding particles on top of the wavefunction:

https://arxiv.org/abs/1906.10761

Advocates of both theories say that they predict different results than quantum theory than some experiments, so they are alternatives to quantum theory. Bell's theorem implies that if you hava a theory where the results of an experiment are represented by stochastic variables and the measurement devices and particles are not somehow correlated in advance of the measurement, then that theory is non-local. So both spontaneous collapse theories and pilot wave theories are non-local but I haven't seen any explanation of how the correlations arise in either theory.

Another idea that some people have proposed is called superdeterminism. Superdeterminism claims that somehow the particles and measurement devices are correlated in advance of the measurement. Advocates of this idea have no explanation for how their theory is supposed to work (see Section 10):

https://arxiv.org/abs/2010.01324

The two biggest problem with superdeterminism at the moment are (a) the lack of a generally applicable fundamental theory and (b) the lack of experiment.

I suppose that this theory comes closest to your holism idea. If somebody comes up with such a theory at some point in the future it may be local.

If we take the equations of motion of quantum theory without modifying them, then there is an existing local explanation of how the correlations arise that has nothing to do with holism. Quantum theory describes physical systems in terms of Hermitian operators called observables not stochastic variables. In this theory each measurable quantity has multiple possible values and those values can interfere with one another. When information is copied out of a system that suppresses interference between the different possible values of the measured quantity, this process is called decoherence:

https://arxiv.org/abs/quant-ph/0306072

As a result of this process, on the scale of everyday life reality as described by quantum theory looks a bit like a collection of parallel universes:

https://arxiv.org/abs/1111.2189

https://arxiv.org/abs/quant-ph/0104033

This is often called the many worlds interpretation (MWI) but the worlds are a relatively high level emergent feature of the theory and the parallel universe approximation breaks down quite badly in both interference and entanglement experiments. I should note that the PS in the question misrepresents the MWI:

P.S. I am aware of the many worlds interpretation that arguably seems to resolve this impasse neatly. It simply states that everything occurs which removes the vagueness of traditional QM without positing superluminal influences. My question is moreso about how one would resolve this impasse if there are no multiple realities

The MWI does not just state that everything happens. Rather all of the possible measurement happen in the context of a larger structure that constrains how information flows between systems and between different versions of the same system. For example, there is no universe in which I see Schrodinger's cat alive and dead at the same time because decoherence prevents interference between those two states. The explanation of probability in the MWI is also inconsistent with just saying everything happens:

https://arxiv.org/abs/1508.02048

The MWI explanation of entanglement experiments also requires more than saying everything happens. The observables of each system carry quantum information about the system it is entangled with, but you can't get it by measuring that system alone so it is called locally inaccessible information (LIA). The observables of the entangled systems are unsharp so they exist in multiple versions but have LIA that can be carried in decoherent systems because it can't be copied out by interactions. The LIA produces correlations when results of measurements on the entangled systems are compared:

https://arxiv.org/abs/quant-ph/9906007

https://arxiv.org/abs/1109.6223

The only theory that currently gives an actual mechanism for Bell correlations is the MWI. Other theories either say there is no explanation or don't currently give an explanation.