Picturing wave/particle duality

[SimonA]

I need some help understanding the nature of the wave in terms of QM. Many articles and papers seem to use the metaphor of a wave in water, though admiting its inadequacies. And I've seen models from victorian times that showed the wave in terms of a leading edge following a helix like pattern. This latter is obviously inadequate to explain youngs double slit results in terms of achieving interference patterns. So the water one is more useful but it does have the problem that its medium is kind of two dimensional (removing time for the time being), and the wave function itself provides the extra dimension, whereas the reality being described has, from 'our' perspective, a three dimensional medium, and the wave itself creates the fourth dimension we call EM. So we can adapt our imagination and see waves emanating from a point almost as if that point is a planet 'radiating' its atmosphere away in a pattern that's almost like breathing. Of course breathing requires an inward breath and so that's only really a good visualisation for something like the Transactional Interpretation.

But let's forget about dimension for now, after all the maths seems to suggest there are more than space and time, and focus on that old victorian idea of a particle being the leading edge of the wave. We are imediately confronted with a problem. The particle does not go through both slits. When you see the sea, its not uncommon for waves to "break" along a lateral line, it always seems to be right to left but that's probably just the beaches I've been to. But a wave that is breaking has far more effect on a body it meets than one that is just a swell. So in a detector placed at the slits, if the wave in water analogy holds this far when ignoring dimensions, then the detector would only detect the part of the wave that is "breaking".

I realize these analogies are simplistic, in fact I'm working backwards from the fact light doesn't experience time and the concept of extra dimensions, so simplistic is the best I can do in terms of a way to think about these things. It really gets exciting when you consider Neutrinos that travel as the speed of light and so don't experience time, yet still change as they move.

Of course there is something about symetry that seems plain wrong with the idea of a rolling wave front. But if you accept the possibility of extra dimensions, and how crude the visualisations presented even in the best papers are on the actual mechanics of what's happening in something as simple as the double slit experiment, then I'd prefer to think that the macro is full of clues about the micro.

Now we must bring time back in. For EM of any type it doesn't exist. So why do all QM interpretation rely on it so much ? To be fair the Transactional Interpretation is bold enough to push time's arrow out of the picture in considering the whole concept of advanced and retarded waves. And Bohm didn't seem to concerned with making his theories relativistically invariant. But surely a theory on something that doesn't experience time should start at that point, rather than our own perspective where time exists ? Then we can work towards a way of seeing things that do experience time in a fuller way.

We know that the maths, the quantum formalism, is good. And we know that all the interpretations have no real explanatory power in terms that einstein could explain to his waitress. Why are people so attached to the copenhagen interpretation that has spawned so many "New Age" misinterpretations, when those misinterpretations are mainly due to the fact it doesn't explain what happens in the double slit experiment. Observation in terms of physical measurement is an input into the system - of course. But maybe even when the "particle" is detected at one of the slits, its 'wake' also traveled through the other slit ?

Simon

 

[FulhamFan3]

You can't picture it, ever. They have all the properties of waves until you analyze it and then it behaves as a particle. The closest you'll ever come is to visualise it as a packet of waves spread over a finite volume. The point is the wave/particle duality means it either a particle OR a wave. It can change between them but it's not both at the sametime.

 

[SimonA]

No wonder you support Fulham :)

 

[et]

i must chime in and say i think it is extremely difficult (especially for the western mind) to imagine an object that holds two contrasting properties simultaneously. it is much easier for us to view things as 'either, or', not both.
i think this is key when trying to visualize electromagnetic waves.
the problem i have when trying to do this is i see the waves only projecting from a 2d level.
ex. imagine my body is a transmitter and i hold my arm out at 90degrees and this is where the waves emanate. i know this is not the case, and in fact (i suppose) the waves are projected at all angles into space .
its very tricky

 

[SimonA]

Hi Et

That was why I referred to Einsteins waitress. Surely its mainly "tricky" because we don't understand it ?

Simon

 

[jfxjmn]

i think I must agree with Fulhamfan, but I would like to add that it is in the state that you want to observe it in. This doesn't mean that it's both, it just means that it is whatever you are looking for. If the problem is seeing it as both, don't try.

 

[SimonA]

Quid pro quo

Hey you physics people are getting really deep and cosmic sounding man!

If the problem is trying to avoid understanding things, then don't try.

 

[FulhamFan3]

If the problem is trying to avoid understanding things, then don't try.

It's not that we're trying to avoid it. It's that we do understand that we don't understand.

You could take the view of string theory where all particles are vibrating strings of pure energy. That would explain a lot about why a partcle would diffract but doesn't explain to me about why the other slit would affect.

Or there's another view where it's interacting with particles in another universe. I think I heard that Stephen Hawking takes this view seriously.

Then there's feynman's interpretation. where a particle not only goes through both slits but also take an infinite number of other paths. Meaning a particle going through one slot is as plausible as a particle going to the moon and back. All paths cancel out except for the one you observed for the experiment.

I think the most plausible is feynman's where if you think of it as a wave that propagates everywhere, all paths cancel out except one.

 

[Kea]

hi SimonA

It really gets exciting when you consider neutrinos that travel at the speed of light and so don't experience time, yet still change as they move.

Neutrinos don't travel at the speed of light. They have mass.

Of course there is something about symmetry that seems plain wrong with the idea of a rolling wave front. But if you accept the possibility of extra dimensions, and how crude the visualisations presented even in the best papers are on the actual mechanics of what's happening in something as simple as the double slit experiment, then I'd prefer to think that the macro is full of clues about the micro.

Now we must bring time back in. For EM of any type it doesn't
exist. So why do all QM interpretation rely on it so much?

It is in the nature of a localised particle that it travels at a
speed less than c. As you know, noncommutativity of
observables is fundamental to QM. For example, between
\mathbf{x} (static) and \mathbf{p}
(dynamic). It is therefore quite tricky to describe this without
putting time in...

...but as it happens, there is a way to interpret things where
quantum information 'generates its own spacetime'. Consider the
qubit: this is simply \mathbb{C}^{2} as a Hilbert
space with basis | 0 \right\rangle and | 1<br /> \right\rangle. According to:

A modular functor which is universal for quantum computation
Michael Freedman, Michael Larsen, Zhenghan Wang
http://arxiv.org/abs/quant-ph/0001108

one can associate to the state space of a quantum computer built
on k qubits, given by ( \mathbb{C}^{2} )^{\otimes k}, a
disc with 3k marked points, on which there is naturally an action
of the braid group B_{3k}.

In other words, one can use Jones polynomials...the same knot
invariants that get used to describe so-called pure quantum
gravity in three dimensions (that's one time and two spatial
dimensions).

Now recall that the 'wave' is to be interpreted as a probability
density. If we can remove the space on which the wavefunction is
specified, then the probability density does not rely on the
background a priori, but defines the geometry that we observe.

If we have two slits, we should expect to see evidence that the
geometry is 'wavelike' because that is a constraint that we have
put on our observation.

Don't know if this helps.

Kea

 

[SimonA]

Kea

You are a gentleman (or woman), and a scholar :)

Now recall that the 'wave' is to be interpreted as a probability
density. If we can remove the space on which the wavefunction is
specified, then the probability density does not rely on the
background a priori, but defines the geometry that we observe.

This is great. I hope to understand it better soon!

Thanks

Simon

 

[SimonA]

Hi FulhamFan3

Does "weak measurement" change your fundamental adherence to CI at all ? And where exactly is the observer relevant except in terms of the detector made of matter ?

Simon

 

[misogynisticfeminist]

I don't think the wavefunction of a particle and the physical wave of a particle is the same thing, right?

 

[SimonA]

What is "the physical wave of a particle " ?

 

[FulhamFan3]

What do you mean by "weak measurement"? If the experiment is setup as particle source aimed at 2 slits then the observer is at a screen past the slits taking note of where those particles land.

Do you want another interpretation because you think you can predict the result otherwise?

 

[SimonA]

Ever seen this ?

 

[spacetime]

Although it is not necessary to have a picture or model for everything in physics, still it is better to have one. It only helps in its progress. Noharm in trying to visualize things. And there's nothing that can't be visulaized.




spacetime
www.geocities.com/physics_all/

 

[Dennis J. Plews]

waveparticles

Hi All:

What helped me to obtain a satisfactory mental image of this conundrum was remembering Einstein's remark that matter is just lumpy bits of spacetime, the lessons in Feynman's book, " The Strange Theory of Light and Matter", the concepts of loop quantum gravity and the shapes of the "curled up" dimensions of M Theor and Born's interpretation of the Schroedinger/Heisenberg equations ( the wave packet is the particle). Bearing in mind from the teachings of field theory that the wave equation's expanse is infinite, albeit asymtotically diminishing, that a particle can "smell" the area surrounding it (Feynman) becomes more comprehensible. This view also provides a model for understanding non-locality events. Of course, this all requires that we abondon the zero dimensional concept of a point, but nothing ventured, nothing gained!


Dennis Plews
Sarasota Fl

 

[Burnsys]

The "Wavefunction Colapses" when we do a measurement.. what exactly is a measurement?

If in the double slit experimet we just turn off the Wich way detectors at the slits, but we leave them there, the interference patterns disapear too??

another question, inside of a living cell, what dominates? quantum or clasical physiscs??

 

[SimonA]

Thanks Mr Plews for your thoughts.

Burnsys - "a measurement" is what is required to detect a property of the "particle(s)"

On your second point, apart from "weak measurement" which I believe is still controversial, detectors are matter which will absorb the "particle" whether or not they are "turned off". Its a good point though in terms of some of the interpretation of CI you get.

On your last point, both quantum and classical processes are at work. And in the middle are molecules such as proteins that move around a cell like the way cars move around a city. We have no idea really what drives them to do so.

Someone recently introduced be to Shroedingers Negentropy -> http://www.i-sis.org.uk/negentr.php

'Negentropy', as stored mobilizable energy in a space-time structured (organized) system, can be intuitively understood as follows. In an equilibrium system, energy is fixed, which in turn fixes the population of energy levels characteristic of the temperature of the system. In a nonequilibrium system such as the organism, energy is stored over all space-time domains. For a given temperature, the energy stored is no longer fixed, but on account of efficient coupling, becomes transferred to ever larger space-time domains (starting from the photon trapped in photosynthesis, or the energy in food) until all characteristic domains are equally populated. This implies that the organism itself has no preferred levels, its activities spanning the 'quantum' to 'classical', from the 'microscopic' through 'mesoscopic' to the ' macroscopic' in a quasi-continuum of self-similar patterns.

 

[ZapperZ]

Hi All:

What helped me to obtain a satisfactory mental image of this conundrum was remembering Einstein's remark that matter is just lumpy bits of spacetime, the lessons in Feynman's book, " The Strange Theory of Light and Matter", the concepts of loop quantum gravity and the shapes of the "curled up" dimensions of M Theor and Born's interpretation of the Schroedinger/Heisenberg equations ( the wave packet is the particle). Bearing in mind from the teachings of field theory that the wave equation's expanse is infinite, albeit asymtotically diminishing, that a particle can "smell" the area surrounding it (Feynman) becomes more comprehensible. This view also provides a model for understanding non-locality events. Of course, this all requires that we abondon the zero dimensional concept of a point, but nothing ventured, nothing gained!


Dennis Plews
Sarasota Fl

OK, I just can't help but ask this: Aren't you the least bit uncomfortable or even weary, that you are basing your confidence of your ability to explain away this problem on an area that (i) are still FAR from being in an accepted stage (ii) are still not verified empirically (iii) are still undergoing major changes that is still nowhere near a final, coherent form? I mean, REALLY! It's one thing to read about loop quantum gravity and M-theory and "curled-up" dimensions, but to actually use that to comfortably explain away what is essentially a non-problem? That's astounding!

There is no such thing as "duality" of light in QM. Don't believe me? Open a QM text and find where light is described in two different formulations. This duality arises due to our inherent NEED to catagorize something either as a wave, or as a particle, base on the classical wave and particle behavior. You are trying to fit a square object into a round hole. When it doesn't fit, you blame the hole, rather than look at the fact that what you're holding is not MEANT to fit into that hole. Once we all realize this, then we automatically see that there's no "duality" or any problem here!

Zz.

 

[ZapperZ]

Thanks Mr Plews for your thoughts.

Burnsys - "a measurement" is what is required to detect a property of the "particle(s)"

On your second point, apart from "weak measurement" which I believe is still controversial, detectors are matter which will absorb the "particle" whether or not they are "turned off". Its a good point though in terms of some of the interpretation of CI you get.

This is wrong. If a particle such as an electron passes through a loop of wire, it doesn't get absorbed by it. Yet I can still detect its presence via the current in the loop. Unless you do not consider a loop of wire a "detector".

Someone recently introduced be to Shroedingers Negentropy -> http://www.i-sis.org.uk/negentr.php

What you quote is pure quackery. For example:

For a given temperature, the energy stored is no longer fixed, but on account of efficient coupling, becomes transferred to ever larger space-time domains (starting from the photon trapped in photosynthesis, or the energy in food) until all characteristic domains are equally populated.

Other than the fact that this is nothing but goobleygook (the usage of physics words but in very awkward manner), a photon doesn't get "trapped" in anything, other than supercold Cs atom under laser-induced transparency![1] The energy of a photon is absorbed. It goes away! Photon number is not conserved! Saying it is "trapped" implies that its coherency (phase) is preserved! This is bogus!

Again, I suggest that this is all moot if one properly studies QM.

[1] C. Liu et al. Nature v.409, p.490 (2001).

 

[SimonA]

Zz

I have read a few of your posts and so know you are one of the better informed here. But I'm still curious if you could explain Youngs slit experiment in terms of why the "wave" only appears at one slit and/or why the "particle" goes through both slits.

But more pertinantly, when is it that shroedingers cat becomes dead (and smelly ?) or a cute puring little kitty hungry for some fish :)

 

[ZapperZ]

Zz

I have read a few of your posts and so know you are one of the better informed here. But I'm still curious if you could explain Youngs slit experiment in terms of why the "wave" only appears at one slit and/or why the "particle" goes through both slits.

But more pertinantly, when is it that shroedingers cat becomes dead (and smelly ?) or a cute puring little kitty hungry for some fish :)

The wave only appears at ONE slit? Huh?

How about reading this: The interference pattern in the result of, NOT the photon (or any particle you wish you insert in there), but rather the SUPERPOSITION OF PATHS!

People are reading Feynman and citing him left and right, yet, it appears that most of you ignore the most important contribution he did, his path integral method! But if you do not study QM properly, how could you know this? All you care about are the stuff about him that's written in pop-sci books!

Again, READ the Marcella paper that I've cited a gazillion times on here to see how one can painfully derive the 2-slit interference patterns from photons using standard QM! There is no mystery here, especially when one strip away the very stubborn insistence of imposing a classical particle or wave behavior onto a "photon" or any other quantum entity.

Zz.

 

[SimonA]

Who said I was imposing classical behaviour onto quantum entities ? Where ? This is a lazy excuse to lie back and say "ahh its too complicated to understand - just learn the maths". And that exactly why you avoided any reference to the cat.

And why do you get do funny about the idea that the "wave" only appears at one slit ? Do you accept the idea of the wave form collapsing ?

I'm not questioning that the formalism predicts the results of youngs interpretation. I'm asking questions about what's actually happening. Thats what I was hoping for in my first question. The second one I'm still curious about your opinion on.

 

[SimonA]

To ZapperZ

I missed this post where you said this;

This is wrong. If a particle such as an electron passes through a loop of wire, it doesn't get absorbed by it. Yet I can still detect its presence via the current in the loop. Unless you do not consider a loop of wire a "detector".

I was wrong there. But I was answering a question I didn't think I needed to think much about :)

Simon

 

[ZapperZ]

Who said I was imposing classical behaviour onto quantum entities ? Where ? This is a lazy excuse to lie back and say "ahh its too complicated to understand - just learn the maths". And that exactly why you avoided any reference to the cat.

And why do you get do funny about the idea that the "wave" only appears at one slit ? Do you accept the idea of the wave form collapsing ?

I'm not questioning that the formalism predicts the results of youngs interpretation. I'm asking questions about what's actually happening. Thats what I was hoping for in my first question. The second one I'm still curious about your opinion on.

First of all, if you have bothered doing a search on PF about the damn cat, you would have noticed a bunch of my postings on it! I avoided nothing! I've explained, ad nauseum, about the superposition of the cat, the superposition of locations of an electron in an H2 molecule, and the superpostion of current states in a SQUID experiment. I've even pointed out the Tony Leggett paper that practically peel apart this whole thing! After all, many of the impetus for studying the Schrodinger Cat-type states were motivated in a large part by many of his treatese! So read that!

Secondly, you shouldn't be talking about me making lazy excuses when you refuses to put any effort into understanding the formalism. I can't believe you expect to be spoon-fed about the Marcella's paper, for example, that clearly derived the 2-slit interference using just QM formalism - no "duality"! You are also confusing between the wavefunction of QM with REAL waves. These two aren't the same! One would have seen that if one would have looked at it and studied it mathematically!

This means that telling you to study it and understanding the mathematics are CRUCIAL at understanding the "words" and "phrases" that are used to describe these things. If you don't learn anything else from this mindless discourse, at least get the realization that ALL of the concepts, words, idea, and meanings in physics have underlying mathematical description. If not, they are ambiguous and vague, and they would be no different than that quote you cited.

Zz.

 

[Kane O'Donnell]

I'm not questioning that the formalism predicts the results of youngs interpretation. I'm asking questions about what's actually happening.

PLEASE, tell me and the rest of PF what you mean by this. What do you MEAN "whats actually happening". Don't brush it off - heaps of people come onto PF and ask the same questions about QM and then argue with the answers because it wasn't what they were 'expecting', maybe. Tell us what you mean.

Cheerio,

Kane O'Donnell

PS - SimonA, I'm not an American, it turns out...

 

[SimonA]

Hi Kane

I'm not sure where exactly I said you were an American but I'm in no way anti american anyway. Nor Austalians :) I rekon most peoples and places have good and bad and plenty in between.

But still, I want to know what's actually happening in the basic two slit experiment. I admit I'm fairly ignorant on all this. But I'm not stupid. The slit experiment hasn't been explained to me other than, effectively, Feynmans "Shut up and calculate". I've purchased David Bohms "Quantum Theory" to try and understand the formalism better. Einstein recommended it as the best description of the formalism and I tend to go with him as I reckon there are three things that Einstein needed to know and he would bust current theories apart;

1) Entanglement is real
2) The maths describes 5 (in fact 7) versions of 10 dimensions that are resolved into one by considering a "relatively" hidden eleventh dimension.
3) Afshars experiment which IMO does refute complementarity (and the experiment that got him the Nobel prize - the photoelectric effect - like we pushed him away from his greatest works just by giving him that award for his least significant work)

But attempting to read this excellent book has made me realize more than ever that I need to improve my maths before I can hope to explain the formalism in a way that would make sense to both waitress and scientist. Maybe my ideas are plain junk. But I can't find anyone who can explain why they are. Thats all I'm looking for. Some really harsh criticism of why an extra dimensional quantum (EDQ) theory does not unify QM and cosmology.

I don't think people will be able to make a model of a star going supernova until they accept this simple theory. If a star builds up energy in extra dimensions then its going nova becomes natural rather than the strained models made so far.

I'm not being clever, all I'm doing is saying that the maths of M theory and QM, are probably connected to relativity (not a surprise as M theory comes out of QM and relativity!). But I'm not interpreting that in any other way than common sense. Sometimes the maths seems to allow people to get lost. And that's a difficult thing to say for someone who considers numbers in a kind of platonic way. I suspect its Cantors rubbish that leads to this unnecesary Hegelian clash.

Simon

 

[SimonA]

And there is another element I should mention. The essential lack of 'substance' to lower dimensions like space-time. I don't rekon Bohr nor Cramer or Bohm have the real explanation about what's going on. And I loath the point based dimensions that M theorists have got lost in. But it seems to me that every law of nature, if understood correctly, acts exactly the same everywhere in any point in the physical universe. And that sounds kind of holographic to me. When you get to the idea of the information contained within a black hole being described by its surface area rather than its volume, then that seems like a big clue about how dimensions are held together in an extra dimensional model.

I think we know about 1% of everything scientifically, being generous, and I'd love to know more. Either I am wrong saying that, and then I'd like someone to present some kind of evidence that we know anything significant about more than 1% of the universe, or I am correct, and then a dangerous road rises up. All the cranks and needy psychologically damaged individuals rise up and claim their junk based on their own need for the paradise lost described in Genesis gets unwaranted attention. But the heart of science does require honesty. Does anyone have any suggestion about how science can admit its limits in understanding the big questions, whilst not allowing the crazy new agers and creationists that place themselves in between honest religion and honest science to get credibility, when their perspective on truth is so warped ?

I appologise if this is off topic.

 

[NewLocality]

I have been asked the following question regarding Proper Interval locality.

"My question is about the fact that I didnt find anything traveling in your
theory. In the ordinary theory if an atom emits a photon that same atom is
ready to absorb a photon before its "previous" photon has been absorbed by
another atom. My point is that the transaction of energy by photons takes
time, and during that time the energy is not associated with any atom. I
didnt find that part in your article, did I miss it or is there another
solution"

I made the following reply.

An extreme example of the instantaneous nature of the exchange of electromagnetic energy between quantum systems is the Hubble deep field picture. This might help you picture what’s going on.

Firstly let me summarise the predictions of proper interval locality: -
Spatial remote quantum systems (atoms) exchange energy instantaneously (when viewed from the inertial perspective of the energy being exchanged). The energy involved in the photonic exchange process does not have any independent existence outside the donor and absorber systems. The event denoting the emission of energy from the donor system is connected to the event denoting the receipt of energy by the absorber system by a zero interval path. The two events are contiguous in space-time. We can regard the two systems to be super-positioned on each other. This allows the energy of excitation to pass from donor to absorber instantaneously without the need for a carrier particle.

Note the super position of quantum systems is universal; all systems are connected to every other system via many zero interval paths. The essence of proper interval locality physics is to evaluate for any physical configuration how these paths are likely to influence the outcome of observable events.

The Hubble deep field picture is an image of an area of the sky covering 2.5 arc minutes in the constellation of Ursa Major. The image shows about 1500 galaxies from a time when the universe was only a fifth of its present age (assuming the Big Bang to be correct?).

To form this image proper interval locality says that the interval between the charge- coupled device in the Hubble camera and the distant galaxies must have zero magnitude.
The galaxies and the camera are contiguous in space-time. Excited atoms in the far galaxies are super-positioned with the atoms of the charge-coupled device in the camera. Conversely, the atoms in the CCD have presence in the distant galaxy. The energy can pass between the super-positioned systems; that is from a donor system in the distant galaxy to an absorber in the camera. Relative to our inertial reference frame the energy appears to jump 10 billion years and 10 billion light years. Relative to its own inertial frame no time or distance is traversed.

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