The funny stuff aside; how can you "measure" a superposition or how can a measurement be in a superposition? I thought any observation causes the wave function to collapse in a single eigenstate and a measurement, I would think, involves an observation. — Benkei
Now I am not a physicist, but I would remind us all of a conceptual issue that might cause misunderstandings here.
We seem to have a situation where one observer sees a certain situation, and another sees a contradictory situation. A sees p, B sees ~p.
It's worth reminding ourselves that this is not new. The same thing can happen in relativistic physics where one observer will see events in a different sequence to another.
But of course what happens in relativistic is that a set of equations are used to translate between the observations. SO although A sees p and B sees ~p, A will also see that B sees ~p, and B will also see that A will see p.
That is, A and B agree that: A sees p, yet that B sees ~p.
Now it seems to me that objective reality has here not so much been undermined as redefined.
A corollary: this fits in with a view of language, logic and mathematics such that we choose a grammar for our descriptions that suits our purposes. — Banno
The notion rejected here is the notion of absolute, or observer-independent, state of a system; equivalently, the notion of observer-independent values of physical quantities. The thesis of the present work is that by abandoning such a notion (in favor of the weaker notion of state –and values of physical quantities– relative to something), quantum mechanics makes much more sense.
...
Let me summarize the path covered. I started from the distinction between observer and observed-system. I assumed (hypothesis 1) that all systems are equivalent, so that any observer can be described by the same physics as any other system. In particular, I assumed that an observer that measures a system can be described by quantum mechanics. I have analyzed a fixed physical sequence of events E, from two different points of observations, the one of the observer and the one of a third system, external to the measurement. I have concluded that two observers give different accounts of the same physical set of events (main observation).
Rather than backtracking in front of this observation, and giving up the commitment to the belief that all systems are equivalent, I have decided to take this experimental fact at its face value, and consider it as a starting point for understanding the world. If different observers give different descriptions of the state of the same system, this means that the notion of state is observer dependent. I have taken this deduction seriously, and have considered a conceptual scheme in which the notion of absolute observer-independent state of a system is replaced by the notion of information about a system that a physical system may possess.
"I have analyzed a fixed physical sequence of events E, from two different points of observations, the one of the observer and the one of a third system, external to the measurement. I have concluded that two observers give different accounts of the same physical set of events (main observation)." [Rovelli] — boundless
I do take it as a great piece of evidence directly supporting the relational interpretation. I agree in full with the way they interpret it,” he says. “It is fantastic that ‘ideal experiments’ of the past become real experiments of today. — Rovelli in New Scientist (Quantum experiment suggests there really are ‘alternative facts’)
IMO, a weaker form of 'correlationism' is, in fact, right. Let me explain this briefly. First, let's define 'direct knowledge' as a form of knowledge that is not based on inference but it is immediate. I believe that for this form of knowledge the 'correlationist' is right. We cannot 'neglect' its 'perspectival nature'. On the other hand, there is another type of knowledge, based on inference that is necessary for science. For instance, if we accept the reasonable assumption that we can know by inference, it seems hard to deny. We can say that we cannot be 'absolutely certain' about it, but it is difficult to think that all our inferences about something independent from our own perspective cannot give us knowledge. — boundless
If the above is true then we simply cannot have a 'perspective'-independent knowledge. Rather all knowledge is 'perspectival' by necessity. Does this mean that there are only 'perspective' and nothing else? That is: can we still speak about 'absolute' properties of things? For instance, can we speak of an intrinsic property of an object O? Or all properties of O are relational, i.e. defined only in relation to other objects? — boundless
What is fascinating however is that it seems that all this reasoning is suggesting that we should take into account a perspectival thinking. That is, it seems to suggest that all 'true statements' we make are context-dependent, so to speak even if we do not accept the 'correlationist' position. We are always 'forced' to specify the context in which a statement is true. (And also we should not neglect too easily our own perspective!) — boundless
Given the above, how can we make sense of the sentence: 'the universe is 13.8 billions years old'? If we accept Rovelli's interpretation, IMO we cannot even speak of 'the universe as a whole'. Why? Because, there is nothing outside that can be used to define a relation (this is very reminiscent of Kant's antinomies about the universe). So, fine! But as you say cosmology is very effective so it is hard to think that even such statement is perspectival. On the other hand, we should not forget that even that statement is made according to a 'perspective', the reference frame where the Cosmic Wave Background is isotropic, that is the 'co-moving reference frame' (check: https://en.wikipedia.org/wiki/Age_of_the_universehttps://en.wikipedia.org/wiki/Cosmic_time ). So, strictly speaking it is still 'perspectival'. — boundless
The objection against idealism based on the distal occurrence is in fact identical with the one based on the ancient occurrence, and both are equivalent versions (temporal or spatial) of what could be called ‘the objection from the un-witnessed’, or from the ‘un-perceived’. And the correlationist is certainly right about one thing – that the argument from the un-perceived is in fact trivial and poses no threat to correlationism. But the argument from the arche-fossil is in no way equivalent to such an objection, because the ancestral does not designate an ancient event – it designates an event anterior to terrestrial life and hence anterior to givenness itself. Though ancestrality is a temporal notion, its definition does not invoke distance in time, but rather anteriority in time. This is why the arche-fossil does not merely refer to an un-witnessed occurrence, but to a non-given occurrence – ancestral reality does not refer to occurrences which a lacunary givenness cannot apprehend, but to occurrences which are not contemporaneous with any givenness, whether lacunary or not. Therein lies its singularity and its critical potency with regard to correlationism.
We are told that the transcendental does not exist because it does not exist in the way in which objects exist. Granted, but even if we concede that the transcendental subject does not exist in the way in which objects exist, one still has to say that there is a transcendental subject, rather than no subject. Moreover, nothing prevents us from reflecting in turn on the conditions under which there is a transcendental subject. And among these conditions we find that there can only be a transcendental subject on condition that such a subject takes place... In other words, at issue here is not the time of consciousness but the time of science – the time which, in order to be apprehended, must be understood as harbouring the capacity to engender not only physical things, but also correlations between given things and the giving of those things. Is this not precisely what science thinks? A time that is not only anterior to givenness, but essentially indifferent to the latter because givenness could just as well never have emerged if life had not arisen? Science reveals a time that not only does not need conscious time but that allows the latter to arise at a determinate point in its own flux.
The relevant question about our networks of inferential knowledge is whether they are vindicated solely by virtue of being intersubjectively validated or whether a knowledge claim's intersubjective validation tracks how nature behaves. Scientists don't produce theory or experiment, usually, for the purpose[ of intersubjective validation, they validate claims about the world using shared methodologies. Even repeating an experiment is done to assess whether a claim is true, consistent with the available evidence, or neither of these things. — fdrake
Even when all properties are relational, we can still be in the state where Alice agrees that Bob sees X, Bob agrees that Alice sees not-X, or that one was in a superposition or whatever. The general logic here is about as banal as Banno portrayed it outside of the QM context and @Andrew M portrayed it within the context of the paper in the OP. Collapse is observer dependent, great, we have established something about nature. — fdrake
I would remind any reader that a view from somewhere is a view of something. The context dependence of the production of a theory; through whatever intersubjective validation mechanisms you like; does nothing to diminish the truth of well established claims using methods consistent with the theory (or theoretical context). — fdrake
Yes, the calculation of the age of the universe is done with respect to a reference frame in which its expansion is isotropic. But:
You can still make ancestral statements within the frame — fdrake
What this argument reveals is that the conditions of possibility for the sense of ancestral statements require us to be able to think of a world indifferent to any given; any conditioning sensibility or emergent system of intersubjective validation. The meaningfulness of ancestral statements requires us to adjust our sophisticated intuitions about the a-priori nature of the correlation between thought and being to include the ability to interpret, since we inhabit, a world radically indifferent to any conceptual distinction. Nature becomes a curmudgeonly gainsayer who can refuse to yield to any determination of theory or sensibility; it will shout "NO!" whenever it bloody well likes and may not speak our language. — fdrake
Nature becomes a curmudgeonly gainsayer who can refuse to yield to any determination of theory or sensibility; it will shout "NO!" whenever it bloody well likes and may not speak our language. — fdrake
we inhabit a world radically indifferent to any conceptual distinction. — fdrake
Maybe also Andrew M and @noAxioms might find the above linked videos interesting. — boundless
The price to pay for RQM:
We need to get rid of the notion of:
- absolute (observer-independent) state of a system
- absolute (observer-independent) value of a physical quantity
- absolute (observer-independent) fact
The claim of RQM is that if you take this step, everything becomes simpler (cfr: special relativity, and the need of getting rid of absolute simultaneity.) — RQM - Rovelli
What troubles me about this is that, on my understanding of QM, wave function collapse is non-measurable. It is a matter of interpretation, of ontology, not something that can be measured - so strictly speaking it isn't even part of QM. So either this experiment implies less than the MIT pop summary says it does, or I am going to have to radically revise my understanding of QM. — andrewk
(1) Do you believe that ionic bonds happen without human intervention?
(2) Do you believe they happened before the advent of humans? — fdrake
'Everyone knows that the earth, and a fortiori the universe, existed for a long time before there were any living beings, and therefore any perceiving subjects. But according to Kant ... that is impossible.'
Schopenhauer's defence of Kant on this score was [that] the objector has not understood to the very bottom the Kantian demonstration that time is one of the forms of our sensibility. The earth, say, as it was before there was life, is a field of empirical enquiry in which we have come to know a great deal; its reality is no more being denied than is the reality of perceived objects in the same room.
The point is, the whole of the empirical world in space and time is the creation of our understanding, which apprehends all the objects of empirical knowledge within it as being in some part of that space and at some part of that time: and this is as true of the earth before there was life as it is of the pen I am now holding a few inches in front of my face and seeing slightly out of focus as it moves across the paper.
This, incidentally, illustrates a difficulty in the way of understanding which transcendental idealism has permanently to contend with: the assumptions of 'the inborn realism which arises from the original disposition of the intellect' enter unawares into the way in which the statements of transcendental idealism are understood.
Such realistic assumptions so pervade our normal use of concepts that the claims of transcendental idealism disclose their own non-absurdity only after difficult consideration, whereas criticisms of them at first appear cogent which on examination are seen to rest on confusion. We have to raise almost impossibly deep levels of presupposition in our own thinking and imagination to the level of self-consciousness before we are able to achieve a critical awareness of all our realistic assumptions, and thus achieve an understanding of transcendental idealism which is untainted by them.
(3) Do you believe that human ratiocination can find order in nature because the human mind and the regularity in nature jointly participate in some eternal cosmic logos? If so, how do you think that works? — fdrake
(4) Do you believe in anything like the distinction between primary and secondary qualities? Primary qualities being like mass, tensile strength, temperature and so on. Secondary qualities being heaviness, sturdiness, warmth and so on. — fdrake
In principle, it doesn't matter whether it's an 'ionic bond' or any other chemical or physical relationship. The ionic bond is just an illustrative example. — Wayfarer
In response, it is perfectly possible to have a realist view of the empirical domain - the age of the earth, the universe, the solar system and so on. I take a realist view of all such facts. But it doesn't obviate the point, which is that the human mind - your mind and mine - is an essential pole in any such statement, even statements of empirical fact - which is the basic claim of transcendental idealism. So empirical knowledge, even knowledge of the early cosmos, is still the analysis of phenomena, of what appears. — Wayfarer
Sounds like if H is also factorizable into H3 and H4 instead of just H1 and H2, H3 and H4 'exist' as much as the other two, and yet cannot exist in different worlds from H1 and H2, only in different worlds from each other. I think I got the gist of your explanation in your post, but it seems that RQM might suffer from some similar issues.In MWI, there is only a quantum system, the universe itself. Its quantum state is a vector in a Hilbert space.
Now, consider a complex quantum system, that is a quantum system like, say, a pair of particles. Let us call them P1 and P2. To each particle is associated a Hilbert space, say, respectively, H1 and H2. To the total system we associate the Hilbert space, H, which is the tensor product of H1 and H2. So, the quantum state of the total system is a ray in the Hilbert space H, which is 'factorizable' into H1 and H2, the Hilbert spaces related to each particle. Here, the factorization is well-defined by the two particles themselves. — boundless
Don't know what simultaneity has to do with it. Relativity seems to work fine with a defined preferred present, even if there is no way to determine it in SR. I suppose that with spooky action at a distance, a preferred foliation would unambiguously label one event as the cause and the other as an effect, but as the experiment that Wayfarer linked shows, there is no spooky action. The distant person (Alice) can make the measurement and Bob (local) know it because it was a scheduled thing. And yet Bod can measure his half of the pair and verify it is still in superposition. QM demands this, so it is not an interpretation.thing . The OP sort of disproves and spooky action at a distance. Alice knows that Bob will take a measurement in one second, and knows the result she will learn tomorrow when Bob reports it, and yet Bob verifies continued superposition, and then an hour later he actually measures the polarity. The superposition doesn't go away due to Alice's action. Therefore there is no spooky action at a distance. No?Well, I think that probably different 'Copenaghists' would give different responses (after all, there is no agreement among them about the right interpretation of the wave-function). But, I suspect that this problem might be avoided using the same argument that (IMO) is used by RQM, that is, reasoning with 'perspectives'. After I make a measurement, I am sure about the outcome of the other measurement. But until I actually receive the confirmation of it, such an event (the measurement) is outside my perspective.
I do not know however if this argument is really enough to avoid non-locality.
(Note that, more or less, this is the reasoning that is employed to avoid the 'block universe' interpretation of Relativity. In that case, the point is that each 'observer' can define 'its' own plane of simultaneity, i.e. its own present. But if we believe that all these events are 'actually real', then it is not too hard to show that it would imply that we are in 'block world': https://en.wikipedia.org/wiki/Rietdijk–Putnam_argument). — boundless
The table says it denies locality. OK, I see the note [15] which seems to claim a sort of loophole in Bell inequality. I do suppose that relativity has an implication of locality since without it, events with cause/effect relationship are ambiguously ordered. Not sure if relativity theory forbids that explicitly. A nice unified theory would be nice. The sort of 'weak' non-locality required by dBB interpretation claims to be Lorentz invariant, so that means causes and effects are unambiguously ordered, no? Not an expert, but if Alice and Bob both measure their entangled polarities fairly 'simultaneously', it seems the order of events is hardly Lorentz invariant. So maybe I just don't understand that note.As an aside, a note in that table says that the de Broglie-Bohm interpretation is compatible with relativity. This is IMO wrong. The point is maybe that we cannot observe any violation of relativity via the transmission of faster than light signals.
Don't know what you mean by 'reverse polarity', but yes, Alice can take her knowledge of the result and put in on paper and mail it to somebody, and then forget about it, allowing Alice to merge with herself. That's how they do it in the lab. The device that takes the measurement sends the result down the pipe and is afterwards totally unaltered by the result of that measurement. It un-splits, and only the thing 'in the mail' is still in superposition.Those two version of Alice, being in different worlds, cannot communicate or otherwise be aware of each other. But they behave exactly identically because they're keeping that knowledge a secret.
— noAxioms
But note that they're not actually identical since they each have a different memory of what they measured. What Bob can do is reverse Alice's polarity measurement while retaining the record that the measurement occurred, which is identical for both Alices. This means that the two Alices will merge without memory of the polarity result and with all records of the polarity result having been erased. — Andrew M
If Alice discards the result like that, then it wasn't done. Memory of having done it doesn't change that. A mirror doesn't reflect a photon. It measures it and sends a new photon out at the new angle and same polarity, and is afterwards unaffected by having done that. It doesn't count as a measurement since the photon is still in superposition.That is, there will be only one world branch again, with multiple histories, and with the record that a definite polarity result was measured by Alice.
Yes.This is analogous to the double-slit experiment where the single particle detected on the back screen had two distinct path histories (one for each each slit).
Thanks boundless - they're excellent videos and well worth watching for anyone with an interest in the philosophical aspects of QM. Fun quote from Rovelli at 36 mins: "When I told Max (Tegmark) that he was a relationist, he told me that he is going to convince me that I'm, without knowing, a Many World believer. — Andrew M
1. Is this just a semantic difference with Many Worlds? (That is, there are nonetheless many physical branches, but there are only deemed to be facts relative to an observer's branch.) — Andrew M
2. If not, then what is the substantial physical difference and what explains physical interference effects? (Many Worlds would explain it as physical interference between branches.) — Andrew M
Sounds like if H is also factorizable into H3 and H4 instead of just H1 and H2, H3 and H4 'exist' as much as the other two, and yet cannot exist in different worlds from H1 and H2, only in different worlds from each other. I think I got the gist of your explanation in your post, but it seems that RQM might suffer from some similar issues. — noAxioms
Now, I do not know if a version of this problem might appear in RQM (which AFAIK does not even use decoherence). The reason is that in MWI you regard the entire universe as the single 'real system' and you need to add an 'additional structure' in order to decompose the universe into subsystems. In RQM, the subsystems are the 'primary' because they are given by experience (in MWI, instead you try to derive experience from the universal wavefunction).
In other words, factorization is something that you do not need to justify simply because it is so to speak given by experience. (Also the comparison between RQM and Everett's theory in the SEP article about RQM might be interesting here...) — boundless
Ionic bonds happened before the advent of humans, yes or no? Ionic bonding would have occurred even if humans never existed, yes or no? — fdrake
In any case, what is common in Kantian-like philosophies is a sort of paradoxical situation of 'external objects'. Since they are regarded the cause of our sensorial experience, they must exist independently by us as the 'empirical things in themselves' (hence 'empirical realism'). At the same time, however, they are still 'inside' the representation. Check also how Kelley L. Ross deals with this issue of 'empirical realism': http://www.friesian.com/kant.htm#idealism. — boundless
What is remarkable about this description of the modern philosophical conception of consciousness and language is the way in which it exhibits the paradoxical nature of correlational exteriority: on “the one hand, correlationism readily insists upon the fact that consciousness, like language, enjoys an originary connection to a radical exteriority (exemplified by phenomenological consciousness transcending or as Sartre puts it ‘exploding’ towards the world); yet on the other hand this insistence seems to dissimulate a strange feeling of imprisonment or enclosure within this very exteriority (the ‘transparent cage’). For we are well and truly imprisoned within this outside proper to language and consciousness given that we are always-already in it (the ‘always already’ accompanying the ‘co-’ of correlationism as its other essential locution), and given that we have no access to any vantage point from whence we could observe these ‘object-worlds’, which are the unsurpassable providers of all exteriority, from the outside. But if this outside seems to us to be a cloistered outside, an outside in which one may legitimately feel incarcerated, this is because in actuality such an outside is entirely relative, since it is – and this is precisely the point – relative to us.
Ideally I want to know whether you think 'Ionic bonds happened before there were humans' makes sense when interpreted literally, even if that interpretation is misguided or shows an insufficient deference to the role the transcendental subject plays in apperception. — fdrake
Ionic bonds happened before the advent of humans, yes or no? Ionic bonding would have occurred even if humans never existed, yes or no? — fdrake
With decoherence, which is key to my preferred interpretation, collapse does not happen, unless we want to call a rapid but continuous evolution from one state to another a collapse.Whether this collapse has a physical interpretation, and what that physical interpretation is, are where all the knots are AFAIK. — fdrake
Why is the question being asked? What lead to the asking of the question? What is the issue? Isn’t it because physics itself has challenged the idea of ‘observer-independence?’ — Wayfarer
You can’t get a y/n answer to that question. Yes, there is evidence of the history of the cosmos prior to the evolution of h.sapiens . But all of that evidence exists in an interpretive framework which presumes a perspective. Thatt perspective is generally implicit, bracketed out. But physics has made that ‘bracketing out’ explicit - hence the interpretive issue. — Wayfarer
You're continually confusing the ability to conceptualise X with X's existence. — fdrake
If you are operating under the presumption of empirical realism, the literal interpretation of 'ionic bonding occurred prior to the advent of humans' is something which must make sense for you even if you think the claim is false. — fdrake
I am not confusing anything. Why do you think Neils. Bohr found it necessary to say that ‘if you haven’t been shocked by quantum physics, then you don’t understand it?’ It’s precisely because it calls into question our innate realism. You have a commitment to the reality of the domain of sense-experience, but you don’t see the way in which the mind itself imbues that domain with reality. — Wayfarer
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