Quantum entanglement, apparatus and methodology

[Dave Wheeler]

Friends, In The Idea of the World, BK puts a compelling case for contextuality and the implications of non-locality for physicalism. He cites several papers, each one seeming to be prove quantum entanglement in ever sterner experiments. I have to put much stock into the work of these scientists who are clearly highly credentialed, but because I am no physicist, I don't even understand really what it is they actually *do*

Is anyone able to clarify for me *what actually happens* in an experiment? It's useful to continue the conventional Alice and Bob's labs example, when I say that my ignorance is at a basic level...how does Alice create a pair of entangled particles, and how does she give one of them to Bob...in a jar for him to drive to his lab and await further instructions? I put it in those terms to show you just how non-physicist I am (I know there are no jars involved!)! I know lasers and crystals and "probabilities" are involved but that's about it.

[Eugene I]

Dave, you just need to look for some popular explanation of entanglement and QM paradoxes, there is plenty on the inet. However, this whole subject is quite complicated and I don't know if it all can be easily explained in a few sentences. 

One of the latest results of these experiments is this:

https://www.technologyreview.com/2019/03/12/136684/a-quantum-experiment-suggests-theres-no-such-thing-as-objective-reality/

Yet, none of those experiments can actually refute the physicalism. These paradoxes are severe in classical QM interpretations like Copenhagen, but there are a number of QM interpretations where they get resolved, such as Many-Worlds (MWI), QBit/Ithaka, or relational interpretations. These alternative interpretations also avoid the wave function collapse problem. However, except for MWI, all other interpretations suggest that here is no such thing as "matter stuff" and what physics describes is either pure information or pure relations. They are sometimes called "zero-world" interpretations. So, one-world interpretations (like Copenhagen) do not stand, they end up in matter being non-local and run into mysterious "wavefunction collapse in measurements" that noone has been able to explain so far. What is left is either many-world universe or zero-world universe (universe of pure information or relations). Of course, for the latter one you can ask - where or in what "media" this information "resides"? A natural answer would be "consciousness", but physicists are trying to avoid such a far-reaching conclusion and stay on purely mathematical ground: "it's all about information or relations". In other words, it s version of a "matter-less physicalism".

The MWI is the only one that can save "matter" and avoid all QM paradoxes quite elegantly, including the Wiener's friend paradox in the above link. A lot of physicists actually support it. Yet, for many (me included) it feels ugly and ad hoc. 

[Dave Wheeler]

Eugene, you'd be surprised at how difficult it is to find a description of the actual methodology of an entanglement experiment that is being carried out by two laboratories (Alice and Bob's)! 

I can wrap my head around what might go on in *one* lab: a strong electric field is applied to an atom and a photon inside may be transformed into two particles, with positive and negative charges and up and down spins. Let's take that as read. But, how do you get *one* of those ephemeral particles to be transported 15km away to Bob's lab where he can demonstrate that his particle has the complementary charge/spin to Alice's? As I joked: "in a jar?"

I did already follow up on a couple of the papers cited in BK's book, but they seem to assume that the reader already knows the nitty gritty about what goes on, because I couldn't determine their methodology. . And all the sites on the net describing themselves as QE Made Easy don't either. It's quite frustrating because we can't even talk about MWI or Qbit/Ithaka without first understanding, at least roughly, what we're dealing with. 

I read incredibly exciting statements such as this from a New Scientist article: "If previous experiments testing entanglement shut the door on hidden variables theories, the latest work seals it tight", and I can hardly wait to explain this to the few friends I have open to this kind of information. Sadly, if one of them asks me exactly what goes on in the experiment, I'd be at a loss!

[Eugene I]

Well, Dave, QM is extremely confusing subject. As Feynman said "nobody understands QM". So it is not surprising that you cannot find an easy explanation. 

Here is the original paper of one of those experiments so you can see their actual experimental setup:

https://arxiv.org/abs/1902.05080

The evens do not need to be 15 km apart, a few meters is enough.

But again, going back to my first post, all these experiments are paradoxical only in "one-world" QM interpretations (Copenhagen ...) and are resolved in many- or zero-world ones. So, by themselves, they do not debunk physicalism.

[Eugene I]

OK, let me try to explain this Alice/Bob thingy.

Let's say a photon is emitted by an atom. This photon can have two polarization states: 1 and 0 with equal probabilities.

A quantum system of two emitted non-entangled photons will have 4 states with equal probabilities: 00, 10, 01, 11. If they fly in opposite directions 1km apart where Bob and Alice are located, and Bob measures photon 1 and finds that its state to be 1, then the system reduces to 10 and 11. So when Alice measures the photon 2, she can measure either 1 or 0. No issues here.

Now, suppose we make these photons entangled, so only 10 and 01 states actually exist, and the 2-photons system is in a superposition of 10 and 01 states (with equal probabilities). We assume that Bell's theorem is correct (which was proven by a mass of experiments closing all possible loopholes). That means there can not be any hidden variables in the states of each photon carrying the information about which state (10 or 01) was actually there when the pair was created, so the system has to be in a truly random superposition state. Now, Bob measures photon 1 and finds its state to be 1. Then Alice measures photon 2 and she MUST have an outcome of 0. But if Bob result would be 0, then Alice's result also MUST heave been 1. So, the Alice's photon needs to "know" the result of Bob's measurement in order to present itself to Alice with the polarization opposite to the Bob's photon. But how does the photon 2 "knows" what was the result of the Bob's measurement if there are no hidden variables? Somehow, that "information" gets passed from photon 1 to photon 2 over 1 km distance. And if we set up the measurements so that Bob and Alice make them simultaneously (in the Earth frame of reference) then such information exchange would have to be instantaneous. This is what "non-locality" in QM means. It does not contradict the special relativity theory because such setup can not be used for actual transmittance of information between Bob and Alice.   

MWI resolves the paradox by declaring that at the moment of Bob's measurement the universe "splits" into two universes, one with 10 state, and the other one with 01 state of two photons. So in the universe #1 A and B will measure 10, and in the universe #2 A and B will measure 01. And also, there is no wave function collapse in such scenario. A very elegant and ugly explanation :) There is still an explanatory gap in MWI: what is there so powerfully mysterious in a measurement event that it makes the whole universe to split? Each of us splits the universe at an insane rate every moment when we simply look around and see things. Does it make any sense?   

In zero-world QBit interpretation the resolution of the entanglement paradox and wave function collapse is a bit more complicated involving quantum information theory, take a look here:

https://www.youtube.com/watch?v=dEaecUuEqfc&t=26s

 

The bottom line is: there is either many-worlds material world getting split at an  insane rate every time any measurement is performed, or there is a "physical and objective" universe with no material "stuff" made of pure relations or information. If we assume the existence of only one material universe, it has to be non-local. There are still some other QM interpretations claiming that they can resolve the non-locality and collapse with keeping just one material world, but they have their own issues as far as I know. 

[Dave Wheeler]

Eugene, this is perhaps the clearest description I've read yet, thank you. So, there is a beam splitter and that would be equidistant between receiver A and receiver B, and this is why generally a few meters would be used since it's all you need, and you can do that in one lab, as you say. I'm pretty sure that distances in the 12-15km range have been cited somewhere by BK (I'm thinking Geneva?) but I can see why it's not required.

I won't ask how you entangle two photons - as opposed to just splitting them - as I'm sure that's a complicated and lengthy answer!

As to the many-worlds idea, that smacks of desperation doesn't it? It's like multiverse theory to explain the fine-tuning of the universe! They might as well say "it just is" which is the final capitulation.

And that "it just is" reminds me...quick anecdote: a while back I was sharing with a friend my scepticism about the plausibility, in a physicalist world, of the astonishing complexity of life at the molecular level being explicable in terms of undirected laws of physics and chemistry, and of thermodynamics. He said: but nonetheless it happens so the laws of nature must account for it. I repeated: but the laws of physics and chemistry can't account for it - chemical equilibrium would just "sludge up" all molecules in an instant and the organism would collapse to the ground. There must be another law, then said my friend. They need to invent new hidden laws now!

[Eugene I]

Dave, right. Physicalism/realism-based science is always in a process of postponing the answers to fundamental problems and paradoxes, but because they are always in the process of making some progress, they always say: "we are confident that we will solve these puzzles in the future, just be patient". 

[Dave Wheeler]

Yep!

So, Eugene, are we saying that quantum non-locality *should* defeat physicalism but that it is not accepted as proof because of a technicality, an unfalsifiable "many worlds" get-out clause?

Let's recap...from my thoughts (that you helped with) regarding dualism, we can see that there may be two broad challenges we can bring to bear on physicalism, namely 

• the challenge to P>M (the model of mind deriving from matter)
• the challenge to P=P per se (matter as ontological primitive in the first place)

The primary challenge to P>M is the hard problem of consciousness, right?

And the primary challenge to P=P is non-locality, agreed?

If we were to compile a list of our best arguments against physicalism under these two categories (P>M and P=P) what would yours be?

For example, BK's example of brain activity not conforming to reported experience under psychoactive drugs, is a challenge to P>M but not to P=P (i.e. it says nothing about matter's "right to existence")

The anthropic principle, or the fine-tuning of the universe, on the other hand, *is* a challenge to P=P rather than P>M because this specific challenge is asking "can matter, under the known laws of nature, plausibly act this way?" (i.e. can matter combine *by chance alone* to produce the astonishing complexity of everything from the carbon, nitrogen, or water cycles, to the activities of life at the cellular and molecular levels, in a model that precludes intelligent design?)

I would be very interested in your thoughts on this - and everyone else reading - what are your "Top Three" (or more) arguments against P>M and similarly your top three (or more) against P=P?

[Eugene I]

So, Eugene, are we saying that quantum non-locality *should* defeat physicalism but that it is not accepted as proof because of a technicality, an unfalsifiable "many worlds" get-out clause? .... And the primary challenge to P=P is non-locality, agreed?

Dave, there is a good discussion about this subject in a parallel thread

https://groups.google.com/forum/#!topic/metaphysical-speculations/Mv4o3BCBV6c

To consider all scenarios M>P, P=P, P>M, P+M is too much to cover, they all have their own challenges. But to conclude on P=P:

It's not so black-and-white. First, it is good to distinguish between realism and physicalism, although "physicalism" is ambiguous term by itself. But in general "physicalism" assumes the existence of "matter stuff" (whatever it is), while realism is more general and assumes the existence of mind-independent reality, whatever the ontic primitive of this reality might be other than consciousness. For example. in informational interpretations of QM the ontic fundamental is pure information, in relational interpretations - pure relations with no "relata". Non-locality does not refute realism per se and even physicalism if we are prepared to assume that the "reality" or "matter" is simply non-local and non-causal. So, in the P=P framework, there are several alternatives to resolve the entanglement paradoxes:

- many-world matter

- non-local and non-causal matter

- pure information or pure relations (no "matter")

In addition, in the P>M framework, if realism or physicalism is to resolve or avoid the "wavefunction collapse" problem (which is really P-M interaction problem), there are further implications:

- MWI again, or

- non-local non-causal hidden variables 

Physicists came up with hypotheses to explain anthropic principle, such as the bullion of universes each having a unique set of constants, so that we live in a universe where the values of constants are such as to allow for life to exist.

The bottom-line is: none of the above refutes realism/physicalism, because, being a metaphysics, it is non-falsifiable. Realists are very resilient and prepare to go to lengths to save the mind-independent reality, but it doesn't come free, they have to trade something for that - either assume MWI, or to give up on matter, locality, causality and assume hidden variables. There may be other ways around their problems, realists are in a continuous search for them. But either way, the "naive" old physicalism with a single material local and causal world can indeed be refuted. 

But of course, in addition to the above, the major problem with any mind-independent monistic realism (P is fundamental) is the "hard problem", where no one among realists has had yet even a slightest conceivable idea how to even approach it.

PS: may be to be more specific on terminology, Hoffman calls his model "consciousness realism", so may be we should use something like "non-consciousness realism" to refer to the (P is fundamental) ontologies. 

[Dave Wheeler]

Thanks Eugene, I will dig into that thread

The distinction between physicalism versus realism is another layer of the onion I guess (I should have known!) but it sounds like a cop-out to me: "mind-independent reality"? Sounds like matter...and if it's not matter, isn't it a sort of "master" unknown ontic primitive (I'll adopt your shorter version) then, from which matter *and* mind derive? That sounds to me like neutral monism, where the ontic primitive could be information or some other "unknown substance"? Is that fair?

[Dana Lomas]

where the ontic primitive could be information

What is information in the absence of awareness of the information?

[Eugene I]

What is information in the absence of awareness of the information?

 

That sounds to me like neutral monism, where the ontic primitive could be information or some other "unknown substance"? Is that fair? 

 Right. For example, this is literally how they state it:

"mind-independent information as ontologically fundamental" - for realism based on information-theoretical interpretation of QM

"correlations without correlata" - for realism based on relational interpretation of QM

So these are sort of "mathematical universe" versions of reality where some abstract idea (information, correlations) is declared to be the ontic fundamental with no "media" that carries that information or relations whatsoever. There is obviously an explanatory gap of explaining how this information or relations are experienced by our awareness, and how an abstract information or abstract relations can give rise to conscious experiences. This is "brutal emergence" taken to its extreme. In other words, the "hard problem" becomes even harder for matter-less versions of non-consciousness realism.

But a good thing about those developments is that they, unintentionally, allow for easier path of explaining the appearing world in the idealistic ontologies (M>P). If the appearing world does not "behave" like matter anymore, but rather its behavior can be more coherently explained as a flow of information of pure relations, then it is naturally to assume that this information/relations are created and maintained in consciousness, because that's exactly what consciousness is good at - processing information and relations. Idealism is getting relieved from the burden of explaining the "matter", because even realists are abandoning it.

[Martin Helmer]

Dana, your comment triggered a pet peeve i have about the concept of information.

To me, information is "data with meaning".

The statement "mind-independent information " then only makes sense if we posit "meaning" as some mind-independent ontological prime, which is weird.

I don't know; maybe there's definition out there of Information that does not require/imply an "interpreter" or a "meaning-giver", but i haven't seen one yet.

A very selective quote from Wikipedia:  "information is data in context and with meaning attached."

So, I guess my question is: does "mind-independent information as ontologically fundamental" qualify as Realism?

Oh, Eugene, just saw your post. posting anyway.

[Eugene I]

So, I guess my question is: does "mind-independent information as ontologically fundamental" qualify as Realism?

It qualifies as "realism in desperation" :) 

[Dave Wheeler]

Absolutely! What is information without a mind to absorb it and give it meaning? It is meaning-less and thus not information.

And yet, we know how a realist would reply: well, DNA contains information and it does its thing without us being aware of it? And we can program computers to use and produce information. In the latter case, all life may have been wiped out and yet we can conceive of computers rolling on, producing information? No mind there...

So, to a realist, unviewed information is still information. Just as a falling tree in an empty forest still perturbs the air even without an observer to hear it