Cosmology, Quantum Mechanics & Consciousness Message Board › The mechanism within quantum mechanics. What actually happens?

The mechanism within quantum mechanics. What actually happens? Collapse or no collapse?

lan B.
user 10895495
London, GB
Post #: 255

[ .. Continued .. ]

However, the technique of Fourier synthesis does in fact – importing ideas from that 17th century classical modelling – employ the notion of superposition. It is possible to construct Cartesian graphs in which “amplitude versus frequency” taking either time, energy, position or momentum as the variable of interest can be “sharpened up from the “fundamental”, starting, sine wave all the way to a precisely defined square wave in one of the conjugate variables at a time only(!) by superposing harmonics of progressively lower amplitude and progressively higher frequency between symmetrically chosen endpoints of the sine wave. The use of an infinite number of terms gives absolute precision, but now look at the conjugate graph which inevitably tracks this first representation: after superposing an infinite number of terms the conjugate value could lie anywhere. We end up knowing nothing whatsoever about it!

This is where the notion of superposition within QM originates. What you make of it depends upon your own interpretative orientation. (I’ll give you further details about my own if you are interested.)


If that is so..it is a measuring tool and not an actual reality. The particles do not have to literal exist in all possible states at the same time, its just that we cannot as yet measure exactly where they are when traveling and instead just observe the interference pattern which indicates a wave. To me this indicates ...we do not know...not that the particles exist in all states. So I am thinking perhaps the ensemble interpretation works for me regarding the resolution of Schrodingers cat. Otherwise it seems to me there is a confusion of the tools of measurement with what is being measured. I suppose in this view there is no collapse, because there is no superposition in the first place.

I’m afraid that the fact that successive 2-slit-traversing single photons at a time also produce interference patterns exactly as would a multitude (but taking longer, obviously) strongly suggests (IMHO) that we are not dealing with any classically conceivable ensembles but instead that the Schrödinger Equation is the accurate description of some actual, physical entity. I.e. quantum state realism rears its head. Instrumentalism seems impossible to square with such actual measured outcomes.

But I can't help but feel I am missing something though. Perhaps if I keep reading my confusion will abate a bit...but I don't understand why so many assume superposition is literally real in the first place. I know the quantum zeno effect has been observed to be real, so that is one possible reason..but again..couldn't it be that our tools at present make the act of measuring interfere so that the "observation" isn't merely looking but disturbs the natural state?
lan B.
user 10895495
London, GB
Post #: 256

Yes Trisha I remember now that I intended also to comment on your penultimate para, but ran out of time.

Part of my current ontological dispute with Andrew concerns the claim that particles exist. I hereby nail my colours to the mast and aver solidly that I just don't believe in 'em. I mean, are they supposed to be singularities, with all their attendant -- and this time classically generated, mathematical problems ? If not, then they are by default spatially extended, in which case they have an "inside" and an "outside". (They're supposed to be particles, remember!)

Come on! (Sorry, but it has to be said!) One takes it that the walls of these extended polyhedral entities are solid, or something. Strings'n'sealing wax! Bells and whistles! Cogs and pistons! Dammit, Newton's suspicions were after all well-founded! There couldn't be such a spooky, occult force as "gravity", permeating infinitely outwards through empty space, can there? Nosir: We believe in bells'n'whistles; strings'n'sealing wax; cogs and pistons.

I was taught this ditty by my Physics A-level teacher:

"Big fleas have little fleas upon their backs to bite 'em;
and little fleas have lesser fleas, and so on ad infinitum."

Checking online for the origin of this amusing homily I find it's a perversion of an original by Jonathan Swift (1733):

"The vermin only teaze and pinch

Their foes superior by an inch.

So, naturalists observe, a flea

Has smaller fleas that on him prey;

And these have smaller still to bite ‘em,

And so proceed ad infinitum.
"

The only problem is .. We can't find any of this stuff! (Reminds me somewhat of "the search for God" but I sincerely wish to avoid causing any additional, gratuitous offence over and above any which might already have been inflicted.)

So, OK, Will, the hour has arrived! The Ides of March! The quintessential fisticuffs moment has popped up on the calendar! What You See Is What You Get!

(You must admit that such positivist argumentation has more than a ring of truth about it, even though you'd prefer the waiter to offer a somewhat more traditional menu (?!))

Of course, we've all seen electron photomicrographs of molecules or atoms. (I was actually lucky enough -- at the tender age of 16 -- to be thrilled to witness a lattice of gold atoms real-time on the display screen of an electron microscope at UMIST.) Aren't these particles? Well, they're undeniably confined states, and that for well-understood energetic reasons, which, to reiterate, leads me to think along with Sir Roger Penrose that any disruption and subsequent mutual re-alignment ( = "collapse" in traditional terminology) of either some "very small" molecule, atom or indeed any smaller fare involves some in-effect energy-minimisation problem, but because the entanglements are non-local then such a "solution" turns out to be "global".


>Otherwise it seems to me there is a confusion of the tools of measurement with what is being measured.

Very perceptive Trisha. We might make a decoherentist of you yet! Due to non-locality, it is meaningless to (e.g.) ask "where the photon landed" except to specify that it didn't "land" outside specifiable, calculable bounds -- i.e. the baseline spread on the detector target surface (this-time once again classical, because measured) given by the resolution angle available given distance-of-travel from point of emission and the de Broglie relation -- and, given this realisation of the ineliminability of quantum nonlocality -- it isn't too difficult to see that the measurement is actually a detection of some site at which the fresh entanglement of an absorbed photon (the carrier of the electromagnetic field) with an extended array of electric fields within the giant structure of the solid object into which it has disappeared but -- in obedience to the classical imperative of the Principle of Conservation of Energy -- which has marked the energy-transfer event in some discrete, local way.

Roland Omnès in his excellent The Interpretation of Quantum Mechanics about halfway through the book exhibits the somewhat lengthy calculations both of the decoherence times of various systems of varying mass, size and temperature (for instance,some speck of interstellar dust with a mass of 10^-7 kg and at a temperature of 3K takes several thousand years to decohere into some definite position!) and of the physical characteristics which would be demanded of any measuring apparatus which could single out as precisely as theoretically admissible some specific history exhibited within, say, some first-order quantum measurement device such as a small 2-slit interferometer. It turns out that the radius of such a second-order measurer would be around 10^20 x the radius of the currently-observable cosmos!




lan B.
user 10895495
London, GB
Post #: 257

>(for instance,some speck of interstellar dust with a mass of 10^-7 kg and at a temperature of 3K takes several thousand years to decohere into some definite position!)

Sorry, that should of course have read:

10^10 kg.

lan B.
user 10895495
London, GB
Post #: 258

AAarrgghh! .. I meant, of course:

10^-10 kg.

(Believe me!)

lan B.
user 10895495
London, GB
Post #: 259

Hmmm .. I'm beginning to worry that no-one's actually reading my posts. (Who could actually blame them?? sad)

I notice that I've just made another 'orrible 'owler -- well, typo actually, since no-one else has yet spotted it. I hereby apologise for the 3rd time today, and then hopefully I'll be able to leave you in a state of peaceful intellectual indigestion. Here's the howler and its ensuing rectification. (The fact that it's impossible to use superscripts directly doesn't exactly assist matters, of course!) From posting # 254 (a few postings above):

>The crucial point here is that the dimensions of the algebra which precisely defines the lowest physically achievable bound to the uncertainty are always [M][L]^2. [T]^-2. (“Spin” has exactly the same dimensional expression!) If this consequence is not epistemic but ontological—and because it appears within the dimensional expression it couldn’t be anything but ontological – then strict causality drops out of physics! Given that that is the case, the alternative probabilistic description leaves us puzzled as to precisely what “change of state” now actually means within “fundamental” physics!

The dimensional expression should of course have read [M][L]^2.[T]^-1

(Phew! What I earlier gave was the dimensional specification of energy! )


A former member
Post #: 162
Strangely, Ian, although we have a growing list of disagreements, the one you mention is not one of them. I have never to my recollection disagreed with you about the existence of particles. Please point out to me the specific issue on which we disagree. The only comment I may have made about particles is that in the most comprehensive quantum theory, which is quantum field theory, a wave formulation of the physics is mathematically identically equivalent to a particle formulation, and wave/particle duality has its origin in that mathematical equivalence. Though I am not sure if I have said even that until now. I don't remember, so please remind me!

The issues on which I do remember that we have clashed swords over the last year are these:

1. I have said that the explanation of the conscious experience MIGHT involve quantum physics operating in some as-yet unknown way in the brain. You do not believe this and have tried to argue for a classical level of explanation, but so far in my opinion your mission has failed to deliver on that.

2. You believe that quantum physics can all be explained in terms of waves and decoherence. I have disputed that and on two separate occasions now you have fallen silent, apparently because you see the force of my arguments but  have no adequate response. 

3. In order to rationalise your mistaken views about the relevance of decoherence, you have lately been hinting at some type of space-like causality effect. Though when I asked you to clarify you noticeably fell silent. I am waiting for your response because you are certainly wrong about that and if you try to press your idea then I will be ready to draw swords on the issue!

4. I suppose I could add that I also disagree with your verbose, meandering, lecturing style. If you are a college lecturer then i feel sorry for your students. But I do accept that your knowledge of these matters appears to be very detailed and not just cribbed from Wiki or elsewhere. And, to reassure that I can sometimes be nice, I readily concede that this Message Board would be much diminished without your substantial contributions.

PS Trisha, I apologise for the earlier mis-spelling of your name!
A former member
Post #: 50
Mr Buxton, I salute you!

"So, OK, Will, the hour has arrived! The Ides of March! The quintessential fisticuffs moment has popped up on the calendar! What You See Is What You Get!"

What you see is the effects of something.

"(You must admit that such positivist argumentation has more than a ring of truth about it, even though you'd prefer the waiter to offer a somewhat more traditional menu (?!))"

It has a loud clang of pragmatism in my book. I'm not sure about the more traditional menu, I don't believe particles are Smartie like any more than you, or Andrew for that matter, but the maths is 'about' some 'thing'.

In the maelstrom that is my current life that's all I have time for now, but I read with great interest and even occasional understanding your posts.
lan B.
user 10895495
London, GB
Post #: 261

Mr Buxton, I salute you!

That would be with a knuckles-forward V-sign then, I take it!

(Only kidding.)


>"So, OK, Will, the hour has arrived! The Ides of March! The quintessential fisticuffs moment has popped up on the calendar! What You See Is What You Get!"

What you see is the effects of something.

>"(You must admit that such positivist argumentation has more than a ring of truth about it, even though you'd prefer the waiter to offer a somewhat more traditional menu (?!))"

It has a loud clang of pragmatism in my book. I'm not sure about the more traditional menu, I don't believe particles are Smartie like any more than you, or Andrew for that matter, but the maths is 'about' some 'thing'.

Clearly it's about something, otherwise what would be its purpose? .. But it's definitely cheating to insist that some poorly understood physical state S is "a particle" without it being demonstrated to conform to any of the traditional criteria which define particlehood!

Please forgive me for "controverting" once more, but I believe that I can make the point more effectively if I allow myself recourse to controversy (gosh!) for a moment. It's a bit like saying: "Well, God is a person, you know .. That is, he hasn't got a body, and he isn't located anywhere, but rather he's everywhere at the same time. He has emotional drives like a person, but no corresponding facilitative hormones or cerebral hormone receptor sites -- physical correlates which except in this absolutely sui generis situation we positively know are absolutely essential to the experiencing of emotion. Furthermore, he's invisible -- unless he decides to incarnate, which we're told has happened once, bizarrely! (Christian version; no offence to Andrew or those of other faith persuasions intended!) We know that he -- well, I say "he", but it's more like a male persona, rather than anything more substantial -- has emotional drives because his Mission Statement as outlined in his diplomatic brief -- known as "the Bible" -- continually reinforces this point several times per page at just about each of the 700 or so pages that its editions typically contain. We're told that he is, for instance by turns wrathful, loving, self-righteous, compassionate, jealous, and, most of all, desperately in need of continual sycophantic supplication from each of his own Creatures, for all eternity! (Insecure, or what?) Yet -- despite evincing these typically biological drive-states, states which motivate action and therefore essentially cause changes of state within himself, he, bafflingly, remains eternally unchanging. To me all this seems no less contradictory than the claim that "a" "particle" can be "in 2 places at once". (Which statement is of course not to be construed as denying that QM is essentially about discrete transactions; transactions which, because of their discreteness, defy the naturally, otherwise-to-be-inferred, underlying, "take care of itself" mechanism of continuity of motion which belongs to the assumption-set of classical physics, once some state of motion relative to the observer-frame has been established by the application of some force at some time or other.)

Even more important than the foregoing IMHO is the fact that we're not simply deliberating about some clunky pragmatic fudge when whenever we frame the postulates of some physical theory or other. I doubt that it's possible to find a single exception within the history of scientific paradigm-change to my proposed general rule in which the crucial feature of the intellectual transition from the old to the new viewpoint is the abandonment of belief in undetectable entities. (After all, what causal or epistemic role could -- in principle -- any putative "entity" serve if it is in-principle undetectable, because quite apart from anything else, undetectability trivially follows from the condition of complete causal isolation from the rest of reality.

To put it bluntly: If it don't exist, then "it" as sure as hell isn't going to be detectable in principle, no matter how hard you look!


In the maelstrom that is my current life that's all I have time for now, but I read with great interest and even occasional understanding your posts

(At least I exist then.)

A former member
Post #: 51
But it's definitely cheating to insist that some poorly understood physical state S is "a particle" without it being demonstrated to conform to any of the traditional criteria which define particlehood!

Fair enough, the term “a particle” does have baggage, but I don’t think this is where we disagree; we need to find some uncommon ground. I’m perfectly happy with your description of ‘some poorly understood physical state’, I know that feeling, but from someone who declares sympathy with positivism, I’m not clear whether you have made the leap from the epistemological ‘don’t know’ to the ontological ‘don’t exist’. (Just to be clear, I do understand that you have nailed your colours to the mast with respect to particulate particles.)

My position can probably best be described as naïve realism, the sort of thing late Pleistocene savannah wanderers (or something) might have believed. I prefer to think of myself as a thoroughly modern pre-Socratic; I can’t help thinking that there is some ‘substance’ in which properties, mass, spin, charge, you name it inhere. It is this substance that I take you to deny. That being so, I will have to concede that I can’t prove it, it is after all only the measurables that are measurable, but I am genuinely interested in whether you have a physical model of, well, stuff.

I think I take your point about God. And I’m with you up to here:

(Which statement is of course not to be construed as denying that QM is essentially about discrete transactions; transactions which, because of their discreteness,

but this:

defy the naturally, otherwise-to-be-inferred, underlying, "take care of itself" mechanism of continuity of motion which belongs to the assumption-set of classical physics, once some state of motion relative to the observer-frame has been established by the application of some force at some time or other.)

Isn’t it difficult enough in English?

After all, what causal or epistemic role could -- in principle -- any putative "entity" serve if it is in-principle undetectable, because quite apart from anything else, undetectability trivially follows from the condition of complete causal isolation from the rest of reality.

Which, I grant you, is an epistemic no-brainer, but I wouldn’t claim that anything is in principle undetectable unless:

To put it bluntly: If it don't exist, then "it" as sure as hell isn't going to be detectable in principle, no matter how hard you look!

Goes without saying.

I do hope we can find something to have a blazing row about.
A former member
Post #: 164
Or, we could try to find something to agree about. Maybe I should suspend, temporarily, my attacks on Ian. What about the following line of thought?

 A photon is both wave-like and particle-like. It is not 'one or the other'; a photon is 'one and the other'.  The photon can be called a real particle both when it is emitted from an atom (or an electron) and when it is absorbed by another atom or electron. The physical events of the real world are all composed of such particle-like phenomena. We do not see quantum waves, we only infer them. But in between the emission event and the absorption event a single photon has the character of wave, not particle. A single photon particle cannot be measured, observed or detected by any means whatsoever whilst in transit (since otherwise the absorption event would have occurred sooner, at the detection event). Therefore, by definition of what is real (for this purpose at least) the photon does not exist as a particle between the two events, it is real only at those two events of emission and absorption.  A photon is the sum of its aspects, it  starts off localised, then becomes de-localised throughout space, then becomes localised again. That is what photon does and what it is.

In contrast, and to emphasise the difference, we have the wrong idea when we imagine a photon flying along, choosing how to pass through two slits and then reaching its target and making an impact. That is a human-scale picture of a classical particle and it is definitely wrong. Photons are never seen flying through space heading for a target. Photons are definitely not classical particles. A photon has no reality without both emission and absorption events. It is clearly a very symmetrical entity and requires both events for its existence. Therefore when considering wave collapse at this level we can see that even a photon collapses from wave state to particle state in the above terms.   Moreover the symmetrically opposite feature applies at the start when a photon does the reverse trick and 'uncollapses' from a particle emission event into a wave. A photon involves two events and two transitions in form. Curiously, in all the discussion about wave collapse, the preceding wave appearance never gets a mention. 

So I suggest that wave collapse at the level of a single photon is part of what a photon actually is. To get a better idea of quantum behaviour we clearly need to use this more symmetric kind of picture. 

Some implications of this plain and simple description of quantum behaviour are: 

(1) Wave appearance and wave collapse are intrinsic to the very existence of every quantum particle in the universe. They are the reality of what is going on deep down in the quantum world, quadrillions of times a split second all over the entire universe. 

(2) It follows as an obvious consequence that wave collapse has absolutely NOTHING to do with observation by anything or anyone, unless you want to say that an absorbing electron in a photographic plate 'observes' the incoming photon. But that is stretching the English language a bit, is it not?

(3) It does not need to be added that wave collapse has absolutely NOTHING to do with conscious human observation. But there, I have stated the obvious implication anyway, to emphasise the absurdity of that idea. 

(4) The quantum wave function also represents something real, though at a level of reality below what can be physically observed.  The wave function is not just a mathematical description for assessing probabilities; an actual but invisible process must be at work, following its own rules of Nature and generating the quantum physics that we observe.

Any comments on that?
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