> On 9 Aug 2018, at 06:55, Bruce Kellett <bhkell...@optusnet.com.au> wrote:
>
> From: Bruno Marchal <marc...@ulb.ac.be <mailto:marc...@ulb.ac.be>>
>>> On 8 Aug 2018, at 13:50, Bruce Kellett <bhkell...@optusnet.com.au
>>> <mailto:bhkell...@optusnet.com.au>> wrote:
>>> The real problem I see with many-minds theory is that it does not actually
>>> explain the observed correlations. The correlations are presumed not to
>>> exist in reality -- all possible combinations of experimental outcomes
>>> happen, but when Alice and Bob meet, their bodies are still in indefinite
>>> states -- no actual results are recorded by entanglement with their bodies
>>> -- but their minds will be in definite states that agree with the quantum
>>> correlations. This step seems to introduce yet more unreasonable magic into
>>> the 'explanation'. Why are the minds like this when they communicate?
>>
>> Because all Alice and Bob are coupled in that way, by the singlet state.
>> That works if we keep in mind that the singlet state (when not already
>> observed by neither Alice nor Bob) describes an infinity of Alice and Bob,
>> with the spin in all directions, but always correlated.
>
> This is not quantum mechanics. The Hilbert space for the singlet is
> two-dimensional. This space is spanned by two (mutually orthogonal) vector,
> but these basis vector may be chose in an infinity of different ways, all
> describing the same state. There is no way that the singlet is a
> superposition of all possible basis vectors: it is 2-dim, not
> infinite-dimensional.
Due to the fact that a^2 and b^2 can be irrational number, I interpret even any
au+bd has involving infinities of histories possible. The singlet is the
superposition of two base vectors, I agree, but the number of worlds is not
related to the dimension of the Hilbert space.
>
> I think you are describing a particular hidden variable model, in which there
> is actually an infinite dimensional space of the hidden variables, one
> dimension for each hidden vector that picks out a particular spin
> orientation. If we now place an infinite of Alices in this space (by her
> interacting with the singlet, say), the Alice's measurement locates her in
> this infinite space according to the direction in which she made her
> measurement. The other particle of the singlet in this space has an "element
> of reality" corresponding to spin component in the direction opposite to
> Alice's result. When Bob measures this second particle, he gets 100%
> correlated results provided he measures along the same axis as Alice.
OK. (I would not called that a hidden variable theory though, as it is the
description of the multiverse that I associate to the singlet state). If Bob
choses an arbitrary direction, the perfect correlation is transformed into
correlation leading to the violation of Bell’s inequality.
> Before his measurement, Bob is in the same infinite-dimensional space as
> Alice was, so by measuring along the same axis, he self-locates into the same
> subspace, when his particle was already primed to have its spin pointing
> along that axis in the direction opposite to Alice's particle. This hidden
> variable account will work to give the correct correlation for measurements
> along the same axis at both ends.
OK, but same subspace do not entail that the original Alice and Bob will get
the correlated results. It means that they will share the correlated result
only with their respective counterparts.
> But it immediately fails if Bob makes a random rotation before he makes his
> measurement. That will then locate him in a different subspace to that
> inhabited by Alice, so the only possible results he can obtain are up or down
> with 50% probability for either. This does not give the correct correlation
> with Alice for any angles other that 0 or 180 degrees.
But there is no reason that Bob and Alice will ever be able to share those
incorrect correlation result. They don’t know to which worlds they belong.
>
> I had thought through this possible explanation for your insistence that the
> measurements of both Alice and Bob serve only to locate them in the relevant
> subspaces some time ago. But I realized very quickly that this crudest of
> hidden variable models could not work for general magnet orientations.
I will think about this. My feeling is that you are using the usual mind/brain
identity thesis.
> The point about general relative orientations is that the probabilities for
> Alice and Bob getting the same or different results depends on the relative
> angle of their measurements.
Yes.
> In any single trial on an entangled pair, they can get any one of four
> combinations of the possible results.
OK.
> It is the relative probabilities of these results that are crucial for
> reproducing the quantum correlations. And these probabilities depend on the
> relative magnet orientation, a fact which is available only non-locally.
Yes.
> Besides, the above is a hidden variable model that has nothing to do with
> conventional quantum mechanics.
I am not sure what you mean by conventional QM. Without collapse and FTL
potential, or FTL (non-local) hidden variable theory, how do you interpret the
singlet state? Before any measurement I interpret it as a multiverse where the
spin can be in any direction, for both Alice and Bob, but in all branches their
spin are opposite. Then I use the fact that if their measure in non “orthogonal
direction”, they have only partial knowledge, and it concerns only what they
can share with their respective counterpart.
>
>
>> When Alice and Bob make their measurement, if they are space separated, it
>> makes no sense to ask if they are or not in the same world or branches. The
>> result they obtained only entangle each of them with the
>> environment, locally, and that spread on the whole universe (at subliminal
>> speed) so that both of them will encounter only their “correlated”
>> counterparts.
>
> This is just nonsense. A world is defined as a branch of the wave function
> that is fully decohered and disjoint from all other branches.
I disagree.
> Alice and Bob are semi-classical objects, and they do not oscillate between
> branches of the wave function according to random quantum fluctuations of
> their constituent molecules.
Even if that is true, it is not relevant. It is not a question of oscillating
between branches, but of ignoring to which branches their belong before they do
a measurement. I suspect again some naive brain/mind identity link. (Note that
even Everett is ambiguous on this, and some of its motivation consists in
assuring that brain-mind identity link. That cannot work with mechanism, and
eventually we need to take mechanism into account.
> Perhaps the best way to understand the inevitable quantum substructure of and
> macroscopic object is in analogy with statistical mechanics. We do not change
> worlds according to the thermal fluctuations of the molecules in a gas --
> these fluctuations are averaged over (coarse-grained) in the bulk properties
> that characterize the gas, such as volume, temperature and pressure, etc. The
> same is the case for people and other macroscopic objects. They are obtained
> by averaging over the quantum fluctuations of their constituents, and it
> makes no sense to pretend otherwise. We live in a (semi-)classical world in
> which quantum effects are averaged out to insignificance for macroscopic
> bodies. So, if Alice and Bob are together, or share a pair of entangled
> states, they are in the same world by any reasonable definition of a "world”.
I do not think such notion of worlds makes sense, already with just Mechanism.
I suspect we have quite different notion of worlds. I would even prefer to
abandon that term, and use the notion of consistent histories instead, but of
course that too should be handle with caution. I don’t think there is a viable
notion of quasi classical world in any non-collapse theory (or in the
many-dreams interpretation of arithmetic).
>
>
>>> Especially since there are pairs of observers who get results that do not
>>> agree with QM (the 'mindless hulks!’).
>>
>> Alice and Bob always get results which confirms QM. But when they are
>> space-like separated, their consciousness will only be able to differentiate
>> into histories which contains the correlation.
>
> They confirm the correlations because they are always in a world in which the
> quantum correlations hold. It is not a matter of consciousness -- the
> correlations could be calculated mechanically from their lab book results.
> Consciousness need never enter into it.
Not in any magical way, but we talk about the subjective record of Alice and
Bob, which could be replace by any machine. What counts here is that Alice and
Bob obeys QM, then a measurement is only a entanglement + local interaction
propagating that entanglement locally.
>
>
>>> In his 2011 thinking I can only imagine that he would have seen many-minds
>>> in much the same way as he later saw many-worlds -- if appeal is made to
>>> the wave function to make sense of the correlations in many-worlds, then we
>>> have to recognize that this is not a local account since the wave function
>>> is not a local object.
>>
>> I don’t really understand what you mean by that.
>
> That is, in many ways, the crux of the matter. The singlet state of two
> entangled spinors is a paradigm non-separable state: it cannot be written as
> the product of two components, one referring exclusively to particle 1, and
> the other referring exclusively to particle 2.
Right.
> And such a separable two particle state is required if one is to incorporate
> Einstein's concept of local realism.
I disagree here.
> But the singlet cannot be written in that way. The only state that is
> symmetric under rotations about the axis joining the particles is the
> non-separable state:
>
> |psi> = (|+>|-> - |->|+>)/sqrt(2).
>
> No rotationally symmetric separable state can be constructed.
I agree.
> This non-separable state has no dependence on the separation between the
> particles,
I agree. But before any measurement is done, the couple Bob and Alice belong to
each possible situation, including possible non correlated one, in which case,
they will never be able to meet again: only to meet their counterparts.
> so the same entangled state persists for arbitrary separations.
>From the point of view of all observers. OK. That is a relative notion.
> But because particle 2 is intrinsically entangled with particle 1, any
> interaction with one particle necessarily affects the other particle.
I don’t see why you say this, except that you talk like if Bob and Alice where
related to the same branch, which makes non sense to me if they are space
separated.
> Thus the non-separable state is intrinsically non-local.
Yes, but without the need to the FTL if you use the only available mind-brain
identity link possible with Mechanism (in cognitive science).
> If you wanted to make it local, you would have to break the entanglement and
> make it into a separable state.
That cannot work. That violate QM, but that is not needed, it is simpler to
abandon the brain mind identity link. Alice and Bob always belong to infinities
of histories, and totally or partially localise themselves in the branch of the
universal wave.
> And that is not possible in quantum mechanics. If you have a hidden variable,
> or any other system, that does this, then you do not have quantum mechanics
> but some other theory. You would then have to re-establish all the well
> confirmed results of quantum theory in your new theory. Not impossible,
> perhaps, but highly unlikely.
>
>> I am reading your paper, which is nice and well written, but too quick for
>> me on both Tipler and Baylock. It helps me to better see how you interpret
>> the wave, and where we might differ.
>
> Thank you. I hope that I have managed to express myself more clearly than is
> often possible in emails.
You are still quick, but I think we differ, not on QM, but on the theory of
mind used in the non collapse theory. I think we might progress on where we
depart.
>
>> It seems to me that when Alice and Bob prepare the singlet state, even
>> before their long distance separation, there is no sense to say that they
>> are still in the same world.
>
> Of course they can be in the same world.
Alice ((|+>|-> - |->|+>)/sqrt(2)) = Alice((|+'>|-'> - |-'>|+'>)/sqrt(2)), so I
don’t know which worlds you are talking about. They know only that whatever
their measure, will be correlated with what the other is measuring, but the
“other’ refer to infinities of “Bob” before any measurement is done.
> The singlet is prepared at some point between them. The entangled particles
> then separate and reach Alice and Bob respectively.
That makes no sense to me. You talk like if the singlet state fixes the base{
|+>, |->}. I take into account a possible phase factor, which makes the
multiverse rotationally invariant, and this remains true forever in the non
collapse view. The breaking of the rotational invariance below only to the
relative person views, like decoherence.
> Since the particles were prepared together, they separate in the same world
> in which they were entangled.
As long as no-one look at the particles, I don’t see how you select the worlds.
> They cannot jump between disjoint worlds.
They both just belongs to infinity of “worlds".
> So when they meet Alice and Bob (or copies of these two from multiple
> possibilities) their meeting and interacting with the entangled particles
> ensures that Alice and Bob are in the same world when they make their
> respective measurements.
Well, I understand this will re-introduce FTL. I see no QM reason to interpret
the singlet state in the way you do.
> If you try to say anything other than this you are clearly just blowing smoke.
>
>> They are only because their interact and entangle and re-entangle very
>> quickly, but still always at light speed or slower. But even if there is
>> only one cm between Alice and Bob, it makes no sense to say that they are in
>> the same world. They might find uncorrelated results, but, at the speed of
>> alight, each one will only be able to talk to its correctly correlated
>> counterparts.
>
> This is gibberish.
>
>>> The same can clearly be said of the many-minds approach.
>>>
>>> The wave function is not local because the entangled singlet state is
>>> non-separable.
>>
>> OK.
>>
>>> Non-separability means that if you interact with one part of the state, you
>>> affect the whole state:
>>
>> I am not sure you affect any state. You just discover in which branch you
>> are.
>
> There are not many copies of the individuals involved in this scenario. You
> are just obfuscating.
You interpret |+>|-> - |->|+> like this described two worlds, but if that is
correct, such a state would not be rotationally invariant.
>
>> The wave only described a multiplicity of realties(available history), and
>> in this case, when someone, Alice say, look at something inseparable, she
>> got information about her branche(s), and of course she knows that any
>> possible future Bob will have the correlated result. But Bob, if
>> space-separated, might very well find a non correlated result, which means
>> that he localised itself in another branch, where him too will only be able
>> to meet his corresponding correctly correlated Alice.
>
> As I explained above, this is a hidden variable account that does not work
> for general measurement orientations.
Only because you attach the mind of Alice (res. Bob) to a world, when we can
attach them only to worlds (note the s).
>
>> That is how I interpret the QM wave, or the Heisenberg matrices. I am afraid
>> that a “real” treatment would need a quantum theory of space itself, but
>> this needs a solution to the quantum gravity problem.
>
> Maybe a deeper understanding of the nature of space-time would help us to
> understand non-locality. But absent such a deeper understanding, we are left
> with the fact of non-local instantaneous influences. Maudlin in his 2011 book
> makes sense of this via the relativistic "flash" version of the GRW collapse
> theory. That is a possibility, but I reserve judgement. I see no problem with
> co-existence of non-locality and special relativity via the "no signalling"
> theorems.
Non signaling saves only the instrumental part of QM. It seems to me more
realist (and obligatory with mechanism) to abandon the usual identity link
“brain-mind”.
That is a bit what the many-mind theory do, but they correct it in the wrong
direction (to keep apparently the idea that there is still a notion of one well
defined world, which makes already no sense with mechanism).
Note that mechanism itself do not (yet) exclude FTL. It is the “physicist” in
me which is skeptical of any real physical FTL influence.
>
>
>>> the state cannot be split into separate non-interacting parts, one for each
>>> particle in the singlet.
>>
>> I agree with this. But that can be interpreted by the fact that we are
>> ignorant in which branch we are.
>
> No, it can’t
So, just tell me how you interpret the singlet state without singling a base
out of all possible base. That should be possible in the non-collapse case.
Bruno
>
>
> Bruce
>
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