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Superposition in QM

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Skierguy1234
Posts: 1684 - Karma: 88

I'm writing a final paper for my Philosophy of Quantum Mechanics class and hoping by some chance that some people on here have a little understanding of the topic.

My question is about superposition and the two-slit experiment:

Do you think it's plausible to say that an electron creates a wave in the matter around it, causing that wave to pass through both slits in the two-slit experiment, thus altering its path on the other side from its own wave passing through two slits?

I just can't buy into superposition and think this makes more sense

Apr 20 2012 6:31AM
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doitbig
Posts: 4818 - Karma: 315
mmmm two slits.
Apr 20 2012 8:24AM
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thebilly_b
Posts: 12 - Karma: 15
The best way to think of it is that the wave packet represents all the possible positions this particle COULD be at, it goes hand in hand with the uncertainty principle. The best way I like to think of it, is being like a coin in an envelope, we know the coin is somewhere within the envelope, but we don't know where, similarly, the wave packet represents where the particle might be, but we don't know where it is for sure.

So, with superposition, we are diffracting the wave packet, and thus diffracting the possible positions the particle could be at. For instance, the particle could only be at the bright fringes, and not dark fringes, if you think in terms of doing the experiments with light, like Youngs Slits or something.

Hope this helps!
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Apr 20 2012 8:47AM
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Skierguy1234
Posts: 1684 - Karma: 88
i understand that, i'm trying to find another way to explain the phenomena in the two-slit experiment that lead everyone to believe in superposition. I just firmly believe that something can't be in "superposition"
Apr 20 2012 9:13AM
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JamesR
Posts: 3396 - Karma: -12
Keep in mind that physicists didn't run that experiment and say oh this is interesting, let's invent a new field. They've worked very hard to find explanations that don't depend on superposition. Thus far, it's pretty clear that superposition exists. Can I ask why you hold the belief that it can't?
Apr 20 2012 10:17AM
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Skierguy1234
Posts: 1684 - Karma: 88
this experiment and one other are the only things they base superposition off of, I just don't think something can be in two places at once until we measure it and find out its in one place, or has spin up and down in the x direction simultaneously and when we measure it it collapses into having one. I think it always has distinct characteristics of having spin up or spin down, not both simultaneously.
Apr 23 2012 7:42AM
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JamesR
Posts: 3396 - Karma: -12
Why do you reject the evidence for superposition? Do you reject the wave-particle duality completely, or do you think it exists but there might be a better explanation?
Apr 23 2012 10:10AM
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panojibber
Posts: 3382 - Karma: 216
Electrons are both waves and particles simultaneously, and that is where you fail; you are separating particles and waves. Don't try to disprove superposition; its not possible. I don't think you know enough QM to write this paper anyways based on this thread.
Apr 23 2012 11:07AM
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DrZoidberg
Posts: 5675 - Karma: 4,268
If you were to disprove superposition wouldn't that make waves (pun entirely intended) in this area of physics? Schrodinger's cat? From what I've learned so far it seems to be likely that electrons exist as particles and waves and superposition occurs. I'm taking p chem next semester, so I'll probably learn more about this eventually.
Apr 23 2012 11:44AM
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Skierguy1234
Posts: 1684 - Karma: 88
i think the evidence supporting superposition is misinterpreted. We don't understand what is going on so we use superposition as an explanation which holds in microscopic experiments, but when you apply it to reality like schrodinger's cat it just seems stupid. If you put a cat in a box its alive or dead regardless of whether or not you open the box. Superposition says the cat is both alive and dead until the instant you open the box and the cat's superposition collapses into being either alive or dead.
Apr 23 2012 4:16PM
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Skavengers303
Posts: 964 - Karma: 192
I don't think you know enough about the philosophy of science to be giving advice on the topic. science is supposed to be both fallible and testable. people should try to disprove theories because that one of the only ways to strengthen them. and QM is such a strange topic, what better place to start.


OP-I however have very little knowledge on the topic of QM ,besides the very basics, so i really will be little help to you.
Apr 23 2012 4:24PM
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Skierguy1234
Posts: 1684 - Karma: 88
lol you misinterpreted what I was saying. But if your almighty brilliance thinks I don't know enough i'll just not write my paper and curl up in a ball and cry.
Apr 23 2012 4:35PM
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panojibber
Posts: 3382 - Karma: 216
The philosophy of science is called the scientific method. It relies on evidence and experimentation, not philosophical argumentation. Yes, it is good to try to disprove theories, but not when you try to disprove them without experimentation and evidence (and I doubt OP has the resources necessary for such an experiment).
Apr 23 2012 4:36PM
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Skierguy1234
Posts: 1684 - Karma: 88
This is actually for an upper level Philosophy of Science course at Pitt who has one of the top philosophy programs in the country. we talk about the philosophical implications of things such as superposition, many worlds theory, etc.
Apr 23 2012 4:40PM
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DrZoidberg
Posts: 5675 - Karma: 4,268
When applied to a cat in a box it does sound dumb, but isn't that generally because the physics of the common macroscopic world and the really tiny atomic world are quite different? The physics for an electron and a cat don't necessarily have to match up.

I don't exist as a wave and molecule (a very large molecule being substituted for a particle) as far as I know. I'm always a molecule, although, I am always observing myself so my state should be frozen or something? wut. Wonder how that works...

And pano jibber has got it right. Theory is good and highly interesting but it really shines if it can be put into practice. Theorize a way to disprove it then try to disprove it in real life. Although since it's a philosophy class then you'll probably be skipping the real life part, and so can never come to a right answer.
Apr 23 2012 4:48PM
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DrZoidberg
Posts: 5675 - Karma: 4,268
Right as defined by the scientific method, as in being proved with data and experiments and all that jazz.
Apr 23 2012 4:54PM
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Skavengers303
Posts: 964 - Karma: 192
I do agree that experimentation is key to any theory. but it takes philosophy of past results to direct science's path. What i mean is, according to the scientific method, after every experiment one should come up with every plausible explanation for the results of the study, and then do further research to narrow those down. and just because the OP doesn't have the resources to test his ideologies about alternative explanations, it doesn't mean he has no right to question and think about them.


Apr 23 2012 4:56PM
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*Dos*Planker*
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Click for larger image
Apr 23 2012 4:58PM
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Skavengers303
Posts: 964 - Karma: 192
from my understanding, the whole observer part of the experiment is bullshit/bad science. from what i have heard, the only way to detect protons is to have them interact with the detector, which would obviously alter their path.
Apr 23 2012 5:01PM
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Skierguy1234
Posts: 1684 - Karma: 88
yeah they are definitely very different. I just think even in the atomic world things such as electrons are always in one state or the other, not both. To admit superposition in the atomic world leads to implications in the macroscopic world since everything is made up of particles. And to admit that particles behave differently when they know we are watching implies that life is like a computer simulation, almost like a computer realizing its made out of a series of 0s and 1s.
Apr 23 2012 5:14PM
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panojibber
Posts: 3382 - Karma: 216
Technically speaking you do exist as a wave and a particle - your wavelength is just so incredibly tiny that you can't actually oscillate. Large objects do have the same wave/particle duality but they are so big that you can't observe the wave properties.
Apr 23 2012 5:15PM
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JamesR
Posts: 3396 - Karma: -12
What reasons do you have for believing electrons are always in one state or another? What do you mean by state? What implications does superposition have on the macro world? What do you mean by "watching"? Can you explain that computer simulation thing further?
Apr 23 2012 5:28PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
http://youtu.be/8eZqQUdWURs

Embedding is disabled but go to 14:30 and start watching. You might already know everything that's presented in this video but it might help.
Apr 23 2012 5:42PM
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panojibber
Posts: 3382 - Karma: 216
They don't know we're watching... I'm assuming you're thinking of Heisenberg's uncertainty principle. We can't observe these particles directly because the act of observation would alter them so drastically that the results would be meaningless; so we use other methods of observation such as cloud and bubble chambers, along with very precise fields and time-spans to measure these particles. The particles are not "self-aware" so to speak... Unless they actually are and this is something I just don't know about. But I doubt that electrons are self-aware.
Apr 23 2012 5:55PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
But everything is made up of many particles, so doesn't a probabilistic understanding of their behavior work just fine in a macroscopic sense?

I like this thread, don't let it die.
Apr 23 2012 6:00PM
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Skierguy1234
Posts: 1684 - Karma: 88
1. saying electrons are not in one state or another disproves all classical logic
2. by state i mean a pure state as opposed to a superposition state
3. implications on the macroscopic world are complex as shit because atoms are the building blocks of everything
4. by watching I mean observing/performing a measurement
5. superposition states supposedly exist, if we try to watch them exist they collapse into a pure state, meaning they behave differently when we watch them implying they know we are watching them and purposely act differently. it's a complex theory that I would probably not do justice explaining, i do not understand it 100%
Apr 23 2012 6:13PM
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Skierguy1234
Posts: 1684 - Karma: 88
well if you believe in superposition you believe that particles act differently when we observe them because we have never seen a particle in superposition, this is why I don't believe in it
Apr 23 2012 6:16PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
Perhaps it's because of how we observe them and not that they're self aware or playing tricks on us.
Apr 23 2012 6:22PM
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Skierguy1234
Posts: 1684 - Karma: 88
not saying you're wrong, but i think it makes more sense if our observations are right, and they're not in superposition states when we're not looking at them
Apr 23 2012 6:25PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
It might make more sense but experiments have been done to show that's not the case. Einstein believed as you do, but Bohr disagreed. Bohr was ultimately proven right. Did you watch the video I posted?
Apr 23 2012 6:30PM
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Skierguy1234
Posts: 1684 - Karma: 88
that's what bugs me about this, the dudes who are geniuses are the ones who come up with crazy shit like saying that they're self aware. One of Heisenberg's theories is measurement = creation which says that before you perform a measurement on an observable, it doesn't exist. The measurement literally creates the value for the observable being measured.
Apr 23 2012 6:34PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
Make sure you don't discount something just because it immediately doesn't make sense though. Does it make sense to you that time slows down at speeds reaching the speed of light?
Apr 23 2012 6:42PM
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Skierguy1234
Posts: 1684 - Karma: 88
the two slit experiment is the main basis of superposition, there's only one other experiment thats relevant to it, the stern-gerlach experiment. I think there can be alternate explanations for both. yeah i did and that's what my original post was about, now that people are getting into this let me give a little more accurate description:

imagine you wave your hand through the air, if a dust particle is in the air it can be moved by the air your hand is moving; your hand creates an "air-wave" from its motion.

Now imagine an electron being shot at the speed of light. Its motion could affect the particles around it creating a similar "air-wave" just on a particle scale. This "air-wave" would hit the two slits, creating the wave effect you saw in the video, thus altering the electron's path and explaining the wave like pattern. I think the particle doesn't move in a wave, but it's motion creates a wave which then collides with it on the other side of the two slits.


that's what my OP was about
Apr 23 2012 6:48PM
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Skierguy1234
Posts: 1684 - Karma: 88
his theory implies that nothing exists until you observe it, I'm not writing it off because it doesn't immediately make sense, i'm writing it off because I believe what is behind me while i sit at my computer is still there when i'm not looking at it.

The time thing does make sense because if you're moving faster than the speed of light you're technically going into the future, so as you approach it, it makes sense that it's relative
Apr 23 2012 6:54PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
Again you're conflating actions of macroscopic things and microscopic particles. We don't know that they behave the same way. I believe my walls are solid, but the atoms they are made of are almost entirely empty space.
Apr 23 2012 7:24PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
I only read the abstract but this article may prove relevant to your paper. It claims to have caught an atom in a state of superposition.

Apr 23 2012 7:33PM
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DrZoidberg
Posts: 5675 - Karma: 4,268
That makes some sense. Was the two slit experiment done in a good vacuum/magnetic field free environment?

The electron is a moving charge, which should generate a magnetic field right? Is that related anywhere here? If the electron, a charge, was put in a magnetic field it should experience a force and alter it's path. So is it possible that it's own magnetic field alters it's course? I don't know if that's already disproven or even makes any sense... I feel like it's own field either does not, or does so in a constant matter or some way that cancels out.

I think there's a class like this that I can take, I'll have to look into it if you talk about cool shit like this all day. I've already got physical chemistry lined up, and a 4 hour p chem lab and that class would probably be good for a breadth/group requirement. Which I have to take several of.


Apr 24 2012 12:02AM
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Bill.Nye
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Yes. The experiment has been done in a vacuum, and even with only one particle at a time. It still shows an interference pattern, which seems to suggest that even single particles can interfere with themselves (inb4 masturbation jokes).
Apr 24 2012 12:57AM
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Skierguy1234
Posts: 1684 - Karma: 88
this one is interrelated though, because he says nothing about a particle exists until we measure it, so if you don't measure anything about it, it doesn't exist. if the particles that make up the wall don't exist, the wall doesn't exist.
Apr 24 2012 1:21PM
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Bill.Nye
Posts: 4060 - Karma: 2,109
I think you're misunderstanding it (or perhaps I am). It's not that the particles don't exist, it's that they don't exist in any specific place or state. We can only say where the particle is most probable to be until we measure it, and then we can say with certainty where it is.

"if the particles that make up the wall don't exist, the wall doesn't exist."

But they do exist, because the wall is made of billions (possible trillions) or particles, and so we can understand that it exists using the probability model.
Apr 24 2012 1:29PM
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Pussy_Sauce
Posts: 381 - Karma: 23
Then where the hell are they?


Thus don't exist.
Apr 24 2012 1:49PM
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Pussy_Sauce
Posts: 381 - Karma: 23
I've never heard of this explanation and I think it makes a lot of sense. What would the "wave" be if not light?

Is it an electromagnetic wave? Sorry if I am misunderstanding.
Apr 24 2012 1:57PM
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Bill.Nye
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We can only predict where it is most probable to be, that doesn't necessarily mean it doesn't "exist."
Apr 24 2012 2:02PM
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Pussy_Sauce
Posts: 381 - Karma: 23
No it does. It has to be somewhere, that is the flaw in string theory. "Superposition" sounds like a shitty way of saying "eh, we don't really know where it is, but it's there!"
Apr 24 2012 2:04PM
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Bill.Nye
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.....but who says we have to know where that is? The predictions of QM are incredibly accurate for probability computations, so they can't be wholly wrong.
Apr 24 2012 2:10PM
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Pussy_Sauce
Posts: 381 - Karma: 23
Where is superposition?
Apr 24 2012 2:27PM
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Bill.Nye
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In more than one place at once.
Apr 24 2012 2:52PM
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Pussy_Sauce
Posts: 381 - Karma: 23
Exactly. Superposition is lame.



Op WHERE YOU AT??
Apr 24 2012 2:59PM
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Bill.Nye
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You're not making a very compelling argument. Physicists have been examining this since the early 1900s and I'm sure that if they could just walk away from the idea they would, because it would save them a lot of confusion. Perhaps it's not that it's in two places at once, but that we are seeing the particle in two moments of time at once. Einstein showed that space and time are intertwined.
Apr 24 2012 3:02PM
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Bill.Nye
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I read it somewhere but it wasn't a scientific text, I'm just throwing it out there.
Apr 24 2012 3:13PM
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panojibber
Posts: 3382 - Karma: 216
Occam's razor instantly dictates that the theory of two particles existing in different moments of time but being visible right now is completely ridiculous, and that we should accept that the two "objects" are only actually one physical entity. Adding time travel into the equation doesn't provide a solution, just more questions. Besides, the particles have only ONE mass equivalent to the mass of ONE of the particles. It is one thing in two places at the same time.
Apr 24 2012 3:26PM
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