Do I Misunderstand The Double Slit Experiment

[Metric]

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Right, but in entangled state you can not force the electron to be up or down. If you could do that then it would violate special relativity as you could use it to instantly communicate something over long distances.

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Exactly. Hence the difference between quantum information and classical information.

But I only wrote all that to say why he used the word spooky.

And it is spooky, quantum information was exchange, yet it did so instantly.

So violating C is fine, as long as its only done with quantum information.

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The state-of-the-art understanding of this is that no information at all needs to be exchanged between separated entangled particles, and "wave function collapse" (which is supposed to take place in a quantum measurement) is a bit of a red herring.

See, e.g. section 5 of http://lanl.arxiv.org/abs/0708.3535

[gumpzilla]

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What youre talking about here is called the "Delayed-Choice Quantum Eraser" experiment. This is an extention of the beam-splitter experiment. Since we are talking about a double slit experiment in this thread, a simple version of the quantum eraser experiment is all that is necessary to convey my point. Both the eraser experiment you mentioned and the one I delineated are valid in explaining this counterintuitive phenomena.

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Except I believe yours is not physically possible, and mine is. This seems like nittiness, but if there were no way to actually set up an experiment that would measure something like this then it would be a worthless subject to argue. Even in the Bohr-Einstein style thought experiments to try and hash out whether the uncertainty principle made sense, a key point was that they were always talking about real physical systems and behavior.

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It is possible. It's been done. My source is "The Fabric of the Cosmos" page 192.

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The experiment you cite is the one *I* am talking about, which did use parametric down conversion. Your previous comment regarded photons interacting and cameras.

Max, I know about second quantization. I guess you could have some kind of goofy process like virtual pair production, electron interacts with photon 2, annihilation, and then maybe you have photon-photon interaction. The spirit of my comment still stands.

[TheMuppet]

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The state-of-the-art understanding of this is that no information at all needs to be exchanged between separated entangled particles, and "wave function collapse" (which is supposed to take place in a quantum measurement) is a bit of a red herring.

See, e.g. section 5 of http://lanl.arxiv.org/abs/0708.3535

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Thanks.

Very impressive. Although I must admit, its going to take me some time to actually hack my way through all the math.

[thylacine]

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The state-of-the-art understanding of this is that no information at all needs to be exchanged between separated entangled particles, and "wave function collapse" (which is supposed to take place in a quantum measurement) is a bit of a red herring.

See, e.g. section 5 of http://lanl.arxiv.org/abs/0708.3535

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Do you agree with them? (Haven't had a chance to read it yet.)

Do you believe that the entire universe (all of reality) is quantum theoretic? Or do you believe that some information is not quantum information and that quantum theory is an emergent phenomenon that is not truly fundamental?

[ILOVEPOKER929]

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What youre talking about here is called the "Delayed-Choice Quantum Eraser" experiment. This is an extention of the beam-splitter experiment. Since we are talking about a double slit experiment in this thread, a simple version of the quantum eraser experiment is all that is necessary to convey my point. Both the eraser experiment you mentioned and the one I delineated are valid in explaining this counterintuitive phenomena.

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Except I believe yours is not physically possible, and mine is. This seems like nittiness, but if there were no way to actually set up an experiment that would measure something like this then it would be a worthless subject to argue. Even in the Bohr-Einstein style thought experiments to try and hash out whether the uncertainty principle made sense, a key point was that they were always talking about real physical systems and behavior.

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It is possible. It's been done. My source is "The Fabric of the Cosmos" page 192.

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The experiment you cite is the one *I* am talking about, which did use parametric down conversion. Your previous comment regarded photons interacting and cameras.



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Then we just had a misunderstanding. My comments regarding photons interacting with cameras simply reveals my ignorance on how photons interact with cameras. Assuming you are right, I thank you for pointing this out.

[Metric]

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The state-of-the-art understanding of this is that no information at all needs to be exchanged between separated entangled particles, and "wave function collapse" (which is supposed to take place in a quantum measurement) is a bit of a red herring.

See, e.g. section 5 of http://lanl.arxiv.org/abs/0708.3535

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Do you agree with them? (Haven't had a chance to read it yet.)

Do you believe that the entire universe (all of reality) is quantum theoretic? Or do you believe that some information is not quantum information and that quantum theory is an emergent phenomenon that is not truly fundamental?

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Yes I do believe them, and my position is that quantum theory is self-contained -- all classical information is emergent from quantum information (which is well-behaved and evolves locally and unitarily). It is always possible that QM is wrong, but at least it is self-consistent.

[David Sklansky]

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And sending information faster than C is totally ok, as long as its not classical information (spooky action at a distance already says that information can travel faster than C).

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It's unfortunate that Einstein used that phrase. There is nothing spooky about an observation unless we go into it with an expectation of how nature 'should' be. If we go in with 'nature is how we find it' then it wouldn't occur to us to label it spooky. A mystery, since we don't have a grasp of the situation, but nothing more.

Tribesmen attribute thunder/lightening to spooks and DS keeps up our innate animism with the latest mystery. Iow, the OP is nothing more than our 40,000 year old habit showing it's still part of our makeup. There is no sense in which the slit experiment 'violates' any part of reality, merely our preconceptions of it.

luckyme

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You are making a terrible analogy. As I told madnak almost all unexplained events in this day and age don't strike scientists as totally mysterious. For instance if we discovered that two people could truly communicate telepathically it wouldn't be evidence for God. The double slit experiment however, if I understand it correctly, is more than just unexplained. It seems to defy logic, not just science. And it seems to invoke human consciousness.

Also if you claim that no observation is spooky because "nature is how you find it" you are actually spouting the theistic line. Atheists believe that observations must conform to general laws. Willy nilly observations without underlying logical laws (eg the stars lining up to spell Peter 666) are strong evidence of intelligent design.

[madnak]

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Unless you believe in hidden variables, some information has to have been passed between these two photons. Otherwise you wouldn't always get up + down or down + up (you would get an equal distribution of up up / down down / up down / down up).

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I don't claim to understand the math, but this doesn't make sense. Where is information being passed?

One particle becomes "down" and the other particle simultaneously becomes "up." Where is the information passage? You seem to be assuming that when you measure one particle, an "event" happens in that particular physical location, and information about that event has to propagate to the other particle's location. Do you have any justification for this assumption?

The fact that you are performing your measurement in one location seems to imply little about the event. Given that both entangled particles change states simultaneously, it seems more likely that the event is happening in both locations at once, or that the event isn't best interpreted in spatial terms (ie there is no "location" where it is "happening," we just see the effects in the locations of the two particles). Where am I going wrong here?

[madnak]

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As I told madnak almost all unexplained events in this day and age don't strike scientists as totally mysterious.

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No more or less so than the double slit experiment.

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For instance if we discovered that two people could truly communicate telepathically it wouldn't be evidence for God.

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More so than the double slit experiment...

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The double slit experiment however, if I understand it correctly,

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This thread establishes that you do not.

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is more than just unexplained. It seems to defy logic,

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It definitely doesn't seem to defy logic.

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not just science. And it seems to invoke human consciousness.

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What the hell? How does it seem to invoke consciousness? Unless I've missed something very major in this thread, I don't see what consciousness has to do with anything. My suspicion is that you are taking the term "observation" much too literally. "Observation" in the physical sense doesn't mean "conscious awareness."

[luckyme]

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And sending information faster than C is totally ok, as long as its not classical information (spooky action at a distance already says that information can travel faster than C).

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It's unfortunate that Einstein used that phrase. There is nothing spooky about an observation unless we go into it with an expectation of how nature 'should' be. If we go in with 'nature is how we find it' then it wouldn't occur to us to label it spooky. A mystery, since we don't have a grasp of the situation, but nothing more.

Tribesmen attribute thunder/lightening to spooks and DS keeps up our innate animism with the latest mystery. Iow, the OP is nothing more than our 40,000 year old habit showing it's still part of our makeup. There is no sense in which the slit experiment 'violates' any part of reality, merely our preconceptions of it.

luckyme

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You are making a terrible analogy. As I told madnak almost all unexplained events in this day and age don't strike scientists as totally mysterious. For instance if we discovered that two people could truly communicate telepathically it wouldn't be evidence for God. The double slit experiment however, if I understand it correctly, is more than just unexplained. It seems to defy logic, not just science. And it seems to invoke human consciousness.

Also if you claim that no observation is spooky because "nature is how you find it" you are actually spouting the theistic line. Atheists believe that observations must conform to general laws. Willy nilly observations without underlying logical laws (eg the stars lining up to spell Peter 666) are strong evidence of intelligent design.

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wow.
"defies logic" ! how does it do that?
Human logic determines how the universe operates? Isn't it the other way around? Isn't your claim that it should do what we expect the main stumbling block for science over the years? Isn't that what even einstein chocked on?

"Atheists believe..." what silliness is that? There is no belief you can claim if all the info you have is "george is an atheist". Atheism is a statement of one fact and one fact only "george does not believe a (theistic)god exists". There is no reason somebody can't be an atheist and think his dead grandmother makes the wind ... some may actually fit that.

Your 'atheists believe' claim may be confusing the scientific approach of looking for natural explanations.

When the stars line up for the scrabble tournament we can have another chat, but the universe acting at the quantum level differently than what we understand from our rabbit-hunting level perspective sure doesn't factor into deductions we can draw from it.

String theory or branes may move the discussion into new territory, reframing this slit situation out of existence in a sense.

luckyme