Must have gone through one of the slits

  • Thread starter San K
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In summary: I'm not clear on what you mean by "just as a coin cannot be perfect 50-50"- are you referring to flipping a coin a large number of times? If you flip a coin, say, 1000 times it certainly is possible to get exactly 500 heads and 500 tails- in fact, that is the most likely outcome.No, I'm not referring to flipping a coin a large number of times. I'm referring to the fact that you cannot have both sides of the coin perfectly equal. There will be a difference of few atoms here or there.
  • #1
San K
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A buckyball cannot split into two and then reconstitute perfectly

Thus the buckyball must have gone through one of the slit while its associated wave would have passed through both the slits.

Thus, we conclude that, three things happen:

- Buckyball goes through one of the slits (50-50)
- the “wave” splits into two and one goes through slit A
- the other goes through slit B

Now just as a coin cannot be perfect 50-50 the slits cannot be perfect 50-50 hence the interference pattern will never be perfectly symmetric

in addition to this the fundamental inherent randomness in the photon position is also there, however it is perfectly 50-50 symmetric
 
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  • #2
I'm not clear on what you mean by "just as a coin cannot be perfect 50-50"- are you referring to flipping a coin a large number of times? If you flip a coin, say, 1000 times it certainly is possible to get exactly 500 heads and 500 tails- in fact, that is the most likely outcome.
 
  • #3
San K said:
A buckyball cannot split into two and then reconstitute perfectly

Thus the buckyball must have gone through one of the slit while its associated wave would have passed through both the slits.

You're assuming the classical particle idea holds in the quantum world.
 
  • #4
San K said:
the buckyball must have gone through one of the slit while its associated wave would have passed through both the slits.
The latter is certainly true, but there's no justification for the former. There's nothing in QM that says that a buckyball in this state has a position. QM tells you that detection events have positions, not that particles do.

In spite of that, there's nothing in QM that rules out the possibility that particles have well-defined positions at all times. QM appears to be completely neutral on the issue. See the discussion in this thread, in particular post #51.
 
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  • #5
It doesn't split into two; it was always everywhere.
 
  • #6
HallsofIvy said:
I'm not clear on what you mean by "just as a coin cannot be perfect 50-50"- are you referring to flipping a coin a large number of times? If you flip a coin, say, 1000 times it certainly is possible to get exactly 500 heads and 500 tails- in fact, that is the most likely outcome.

No jiving, man, but I once saw a coin land on it's side. We were at an air cadets summer camp and we were flipping a coin to see who had kick-off in final rugby match. They won on the retoss (which didn't happen until everyone had a look at it on it's side), but we won the game.
 
  • #7
Fredrik;

I know we have some similar thoughts on this, but wouldn't Bohmian mechanics or some loophole in Bell Inequalities have to be true for the particles to have definite position and momentum at all times?
 
  • #8
Fyzix said:
Fredrik;

I know we have some similar thoughts on this, but wouldn't Bohmian mechanics or some loophole in Bell Inequalities have to be true for the particles to have definite position and momentum at all times?
Yes, something like that. This was mentioned in the post I linked to.
 
  • #9
Fredrik said:
Yes, something like that. This was mentioned in the post I linked to.

Ah, sorry I didn't check the post before now.

Do you agree with me now that Bohm is better than MWI if one insist that the wavefunction is ontological?
as Bohm can atleast derive Born Rule and get determinate outcomes.
 
  • #10
Not sure. I don't know much about Bohmian mechanics. I know roughly what it's about, but I still haven't studied the details.
 
  • #11
Check the wiki on it or the Mike Towler introduction to it, it's probably the best intro to Bohm.
 
  • #12
I own the book by Holland. Both Demystifier and Zenith8 recommended it, and they also gave me some suggestions about what parts of it are important. So when I decide that it's time, I'll start there.
 
  • #13
Sounds good.

I'm personally not sure.

For some reason my intuition says that there may come along a discovery that makes everything sensible again.
 
  • #15
Explanations don't need to be sensible to be correct.
 
  • #16
HallsofIvy said:
I'm not clear on what you mean by "just as a coin cannot be perfect 50-50"- are you referring to flipping a coin a large number of times? If you flip a coin, say, 1000 times it certainly is possible to get exactly 500 heads and 500 tails- in fact, that is the most likely outcome.

I am referring to the fact that you cannot have both sides of the coin perfectly equal. there will be a difference of few atoms here or there.

you would have to flip the coin, say a trillion times, to see which side is "heavier"
 
  • #17
StevieTNZ said:
You're assuming the classical particle idea holds in the quantum world.

60 atoms is not quantum world, however (some of) the waves emanating/associated with the buckyball might be

thats why i am thinking that:

the 60 atoms went together, as one piece and the (associated) waves could have split
 
  • #18
San K said:
60 atoms is not quantum world,
If you get the typical "both slits open" interference pattern, it is. I read about a double-slit experiment with C70 molecules where the interference pattern looked less like the "both slits open" pattern and more like the "one slit open at at time" pattern the more they increased the density of the surrounding air. What this shows is that it's not the number of atoms that determines if it's "quantum world" or not, it's how strongly the system interacts with its environment.
 
  • #19
San K said:
60 atoms is not quantum world

What basis do you have for that statement? Much larger coherent systems have been demonstrated, such as BEC condensates. Furthermore, the fact that the buckyballs exhibit interferes demonstrates that they *are* in the quantum world much more effectively than any argument based in theory.
 
  • #20
Fredrik said:
If you get the typical "both slits open" interference pattern, it is. I read about a double-slit experiment with C70 molecules where the interference pattern looked less like the "both slits open" pattern and more like the "one slit open at at time" pattern the more they increased the density of the surrounding air. What this shows is that it's not the number of atoms that determines if it's "quantum world" or not, it's how strongly the system interacts with its environment.

agreed...

however its the waves that might be going through both slits, how can the molecule?

how can a molecule split into two or simply disappear from time-space? and later appear at the detector

this, i think, is better explained by molecule going through one of the slits and waves interfering AND effecting the molecule

photon "splitting" into two is still somewhat acceptable...because its a quanta of energy...but a molecule ...with 30-75 atoms...having their own individual configurations (or spatial position)
 
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  • #21
San K said:
agreed...

however its the waves that might be going through both slits, the molecule cannot

how can a molecule split into two or simply disappear from time-space? and later appear at the detector

this, i think, is better explained by molecule going through one of the slits and waves interfering AND effecting the molecule

photon "splitting" into two is still somewhat acceptable...because its a quanta of energy...but a molecule ...with 30-75 atoms...having their own individual configurations (or spatial position)
Statements like that aren't justified by QM. There's nothing in QM that says that particles have positions. (See the thread I linked to earlier). QM doesn't say that the particle goes through both slits. It doesn't say that it goes through one or the other. It does however say that if it has a position, and it goes through one or the other, it has to behave in a very strange way, e.g. as described by Bohmian mechanics. (What you're describing sounds more like Bohmian mechanics than like QM. It's one way to think about QM, but it's not the only way).

Of course, no one ever says that a molecule breaks in half to interfere with itself. The claim would be that the entire molecule goes through both slits (but I don't think this statement makes much sense either). And no one ever claims that a molecule needs to disappear from spacetime and then reappear for the interference pattern to show up.
 
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  • #22
Fredrik said:
Statements like that aren't justified by QM. There's nothing in QM that says that particles have positions. (See the thread I linked to earlier). QM doesn't say that the particle goes through both slits. It doesn't say that it goes through one or the other. It does however say that if it has a position, and it goes through one or the other, it has to behave in a very strange way, e.g. as described by Bohmian mechanics. (What you're describing sounds more like Bohmian mechanics than like QM. It's one way to think about QM, but it's not the only way).

Of course, no one ever says that a molecule breaks in half to interfere with itself. The claim would be that the entire molecule goes through both slits (but I don't think this statement makes much sense either). And no one ever claims that a molecule needs to disappear from spacetime and then reappear for the interference pattern to show up.

ok...you mean you are on the Copenhagen team and i am on the Bohemian one? shall we pick our flags and mascots too?...:)

i don't like the idea of "shut up and don't ask/talk"...about what happens inbetween...
 
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  • #23
Perhaps its not a particle, but a wave in between? If it split in two, it'd still be a particle wouldn't it?

Edit: may I also suggest chapter one of 'Quantum Physics: A First Encounter' by V. Scarani.
 
  • #24
San K said:
ok...you mean you are on the Copenhagen team and i am on the Bohemian one? shall we pick our flags and mascots too?...:)

i don't like the idea of "shut up and don't ask/talk"...about what happens inbetween...
Maybe cheerleaders too.

I'm not asking anyone to shut up. I'm just trying to get people to realize that a) QM doesn't contain the answers, b) the only thing that can answer a question about reality is a theory, and c) this means that we would have to use some other theory than QM.

So if you want a different kind of answer to questions of the "what really happens?" type, you're going to have to find a theory that answers them first.
 
  • #25
Fredrik said:
Maybe cheerleaders too.

I'm not asking anyone to shut up. I'm just trying to get people to realize that a) QM doesn't contain the answers, b) the only thing that can answer a question about reality is a theory, and c) this means that we would have to use some other theory than QM.

So if you want a different kind of answer to questions of the "what really happens?" type, you're going to have to find a theory that answers them first.

there is no dearth of theories...;)
 
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  • #26
StevieTNZ said:
Perhaps its not a particle, but a wave in between? If it split in two, it'd still be a particle wouldn't it?

Edit: may I also suggest chapter one of 'Quantum Physics: A First Encounter' by V. Scarani.

you mean to say a molecule with 30-70 atoms travels as a wave and reconstitutes, back, perfectly, to a molecule (with all electrons, neutrons etc in the right spatial arrangement and bonding) when detected?
 
  • #27
San K said:
there is no dearth of theories...;)
There isn't even one candidate theory of what's really going on that makes different predictions than QM.
 
  • #28
San K said:
you mean to say a molecule with 30-70 atoms travels as a wave and reconstitutes, back, perfectly, to a molecule (with all electrons, neutrons etc in the right spatial arrangement and bonding) when detected?

Yeah. You seem to be assuming the classical particle notion applies in QM. Please read chapter one of Quantum Physics: A First Encounter for more detailed information.

And as I said earlier, an explanation doesn't need to be sensible to be correct.
 
  • #29
Fredrik said:
Statements like that aren't justified by QM. There's nothing in QM that says that particles have positions. (See the thread I linked to earlier). QM doesn't say that the particle goes through both slits. It doesn't say that it goes through one or the other. It does however say that if it has a position, and it goes through one or the other, it has to behave in a very strange way, e.g. as described by Bohmian mechanics. (What you're describing sounds more like Bohmian mechanics than like QM. It's one way to think about QM, but it's not the only way).

Of course, no one ever says that a molecule breaks in half to interfere with itself. The claim would be that the entire molecule goes through both slits (but I don't think this statement makes much sense either). And no one ever claims that a molecule needs to disappear from spacetime and then reappear for the interference pattern to show up.

But the entire molecule as quantum field can really break in half at the slits and interfere with itself. At the detector, what produce detection events are existing electrons. The original molecule being quantum field at the start (particle being not true) are smeared all over the detectors (here there are no quantum collapses). I find this theory of Neumaier interesting as it can explain it clearly if true. Can you refute this?
 
  • #30
StevieTNZ said:
Yeah. You seem to be assuming the classical particle notion applies in QM. Please read chapter one of Quantum Physics: A First Encounter for more detailed information.

And as I said earlier, an explanation doesn't need to be sensible to be correct.

if the explanation is not going to be sensible then i'd rather go with mine than someone else...;)

as i said...i can buy a photon splitting into two waves...but not a molecule

its possible that photon's movement through the slits is a bit different from the buckyball's
 
  • #31
Fredrik said:
There isn't even one candidate theory of what's really going on that makes different predictions than QM.

wait till you hear my hypothesis about a dimension outside space-time...it explains everything within QM...lol..;)
 
  • #32
San K said:
i can buy a photon splitting into two waves...but not a molecule

its possible that photon's movement through the slits is a bit different from the buckyball's

I am selling photons! :smile:

For purposes of this analogy, the process is the same for the buckyball. See here:

http://hexagon.physics.wisc.edu/teaching/2010s%20ph531%20quantum%20mechanics/interesting%20papers/zeilinger%20large%20molecule%20interference%20ajp%202003.pdf
 
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  • #33
DrChinese said:
I am selling photons! :smile:

For purposes of this analogy, the process is the same for the buckyball. See here:

http://hexagon.physics.wisc.edu/teaching/2010s%20ph531%20quantum%20mechanics/interesting%20papers/zeilinger%20large%20molecule%20interference%20ajp%202003.pdf

ha ha...ok...i will have to stop buying photons...;)

great paper...however it does not agree/disagree with the idea that the molecule might have passed through one of the slits and the waves through both...

thus...for both photon and buckyball...i think ...they pass through one of the slits and their associated waves through both and these waves effect the "solid" part of the photon/buckyball
 
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1. What does "must have gone through one of the slits" mean in the context of science?

In the field of quantum mechanics, "must have gone through one of the slits" refers to the phenomenon of a particle exhibiting both wave-like and particle-like behavior when passing through a barrier with two or more openings. This is known as the double-slit experiment.

2. How does the double-slit experiment work?

In the double-slit experiment, a beam of particles (such as electrons or photons) is directed towards a barrier with two narrow slits. On the other side of the barrier, a screen is placed to detect the particles. The particles passing through the slits create an interference pattern on the screen, indicating their wave-like behavior.

3. What is the significance of "must have gone through one of the slits" in quantum mechanics?

The concept of particles exhibiting wave-like behavior in the double-slit experiment challenges our understanding of classical physics and the idea of particles having a definite position and trajectory. It suggests that the behavior of particles is probabilistic and can only be described by wave functions.

4. Can particles really pass through both slits at the same time?

In the double-slit experiment, particles do not actually pass through both slits at the same time. Rather, they exist as a wave of probabilities and can pass through either slit until they are observed, at which point they collapse into a single position. This phenomenon is known as wave-particle duality.

5. How does the double-slit experiment relate to the concept of superposition?

The double-slit experiment is a prime example of superposition, which is the principle that a particle can exist in multiple states or positions at the same time. In the experiment, the particle exists as a wave of probabilities, occupying multiple positions simultaneously until it is observed and collapses into a single position.

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