Re: [Fis] Quantum info

From: John Collier <collierj@ukzn.ac.za>
Date: Wed 21 Jun 2006 - 16:37:54 CEST

At 02:40 PM 2006/06/21, Arne Kjellman wrote:

The realist�s riddle and the Foundations of Information Science<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

It seemed Andrei in the beginning opened the door to a discussions about the foundations of science, in particular information science:

>Any careful analysis of this situation implies immediately that the whole project  �Quantum Information� should be based on more solid foundations. We recall that >quantum mechanics by itself is a huge building having the sand-fundament � the orthodox Copenhagen interpretation. On one hand, there was created the >advanced mathematical formalism (calculus of probabilities in the complex Hilbert space) giving predictions which are supported by all existing experimental data. >On the other hand, it is still unclear why this formalism works so well and moreover it is not clear what it really predicts, because by the orthodox Copenhagen >interpretation (which is the conventional interpretation) quantum mechanics is not about physical reality by itself, but about just our observations (of what?). >Problems which were of a purely philosophic interest during one hundred years became technological and business problems.  (Yes and its seemed we for some >reason lost the interest in the philosophic questions � but I think it is simply pushed into the background because the realists cannot straighten out the puzzle. AK)
>Therefore �Quantum Information� gives a new great chance for reconsideration of quantum foundations. All unsolved problems of quantum foundations are >essentially amplified in the quantum information project.

 

After this clever remarks it seems to me the list discussion has been pushed into a discussion between realist defenders � sort of neglecting other possible points of view � which make them into rippels on the surface of classical knowning.

 

To my mind these discussion can go on for ever and in vain � and science we will not proceed an inch until the day we are prepared to accept this (simple) fact that human knowing is in principle subjective. There are several stronger reasons but the success of Copenhagen interpretation to reject the human possibility to attribute ontological features to the presumed reality. My claim (and SOA�s) is that no coherent definition of information is possible as long as we keep on trying to make reference to a �reality� that is unknowable in principle. Information relates to the speaking (modelling) knower � and what is in his mind (his experience), just as Bohr says. However his way of reasoning does not only apply to QM � it applies to all forms of knowing.

 

 

To pinpoint the situation let us consider the realist�s dilemma:

 

A human knower first of all needs a MODEL OF HIS MIND in order to consistently describe an ontological reality. However he has no model � and cannot even consistently dig one out.

 

To contemplate this situation:

 Assume I can identify a part of space-time, call it O (let it be modelled by a cube of space-time, cloud of matter, a mathematical point or even a thing � no matter). The crucial question is as to whether O can be said to emit a signal that tells me anything about O � i.e., some feature (property) beside the name O I have attributed to it. The assumption that this is possible lies at the heart of IS i.e., we therefore say that such signals contains �information.� This is the equivalent to assume O is the bearer of such eventual ontological feature and such a feature should then, according to the objectivist (and realist) be considered a pre-�given� feature � or independent of the individual observer observer-independent (exist prior to the knowledge of the knower). One might then ask who this very knower is � and what is the point with human beings to search for the ability to make a similar interpretation. But let me leave this unsolvable question and proceed.

 

Let us instead ask: Is my assumtion of a pre-given feature of O correct?

In order to compute some feature (property) of this is presumed entity O I then need to know what has happened to the signal on its way from O to my consciousness � no matter whether it is a quark, particle, thing or even a bare state transition (assume it to be a state transition ST).

The only way for me to find out how the human apparatus of perception has influenced ST on its way to consciousness is to �send a similar� test signal the same way through my apparatus of perception and compare the original test signal with the received test signal (under the assumtion that the apparatus is stable). Then and only then he can compute a model of my own perceptual apparatus. However such an act of computing is not possible until I know the original test signal � and this is not possible because I have no model of my perceptual apparatus. (This impossibility of comparison is most stikingly reflected in the human monistic situation: There is only one percept!)

What I can do in this embarassing situation is to assume the test signal to be �known in advance� i.e., pre-given. This clearly is misleading since I then assume what I want to show. There is simply no way out if this dilemma but assuming that the features of O are pre-given � but such an assumption is also clearly misleading � for exactly the same reason. The realist is caught in inconsistency.

 

I can see no way out of this dilemma. Can you? Or maybe I am mistaken?

Arne, colleagues,

I don't think that this is an argument for antirealism, but for skepticism. At least it can be made out that way, so there is another alternative. The choice is not between just either we can check our representations against the external world or we only have constructions (or models) to rely on, but also we can hold our models to be falsifiable, and withhold final judgement (this was Hume's route). This position has a very old argument in its favour. The constructivist deviation is very recent. The problem with it is that our models may contain information about the outside world, so to dismiss them as not having that, and judging reality only on our models is equally unjustified and misleading.  There is an argument known to the Greeks, called the Diallelus (the wheel). There is a discussion of it in Nicholas Rescher, Methodological Pragmatism, New York University Press (1977) pp. 15-18. The basic idea is that we have a means of judging truth, or at least acceptability. Call it C. C can be any method you like, simple or complex; it does not matter to the argument. Now we ask if C is justified. Either the justification is in terms of C, which is circular, or in terms of some C', different from C. If the latter, we need to ask (if we did at first for C), is C' justified? Then we are back on the wheel, and so on. Your argument, Arne, can be put in these terms: Let O be the truth, and C be our perceptual apparatus; then we can know O only through C, but what validates C? We are on the wheel, not on the route to taking models to be the essence of reality. This can be seen easily. Suppose that we have a criterion C for judging if our models are acceptable. What justifies C? We are back on the wheel. I see no advantage in retreating to models as the epistemic ground, and it smacks of a sort of verificationism to me. In any case, it adds an epicycle to the problem that can be dealt with just by acknowledging that perceptual apparatus and models are part of the information we have, and we need to be sceptical about whether we are dealing with information from the world or from our C in this case. Then we can get down to the business of trying to figure out how to distinguish the two classes of information (externally originated and internally originated). The first step, I think, is to deny that we have any evidence that there are things in themselves out there; we cannot, by postulation, have information about them, only information transferred from them through an information channel, which invariably adds noise, some nonrandom. So at best we have access to information that forms patterns, some perhaps real and objective, other parts artefactual. Is there a criterion for distinguishing artefactuality from reality? Certainly not some C that is infallible, or we are on the wheel, but there might be criteria that work fairly well as long as we don't get all paranoid about certainty. In traditional science, invariance under transformations of models has been an important criterion (Galileo, Einstein), but certainly not the only one. It seems to me that it can be applied to QM through a structuralist approach to QM.  I don't expect that this will move committed inernalists, constructivists, antirealists and antimodernists (it's too early or impossible to know what postmodernism would be -- see Bruno Latour, We Have Never Been Modern, Harvard UP, http://www.hup.harvard.edu/catalog/LATWEH.html). I colleague of mine, antirealist historian -- Maggie Osler, remarked before examining a realist MA thesis with me, that she thought that being a realist or antirealist was genetically determined, or at least innate. She may have been right. In any case, the same problem of finding invariances applies to the antirealist -- they are of great scientific interest for whatever reason, but it is harder to justify.

As I have mentioned previously, a number of us are producing a book What's wrong with things?: Information-theoretic ontic structural realism, that addresses QM this way, among other subjects. If anybody would like to read and comment on the manuscript, please get in touch with me. It is in revision right now, but any input we can get from this esteemed group would be valuable. This book relies on Peirce for one major premise, but does not investigate Peircean semiotics, which I think is required for a more complete answer to Arne's question of a way out of the dilemma.

Cheers,

John

---

"The agility of the tongue is shown in its insisting that the world depends upon it." Charles Peirce CP 8.83 (1891).
Prof John Collier                    collierj@ukzn.ac.za
+27 31 260 3248 Fax: +27 31 2603039
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Received on Wed Jun 21 16:52:35 2006