# Finding Wave Function Collapse

1. Nov 13, 2005

### Macro

Scientists wan't to know where wave function collapse occures. I have found at least one.

Take the experiment of shooting electrons through two holes that are close together and seeing where they land at a detection screen on the other side. If you shut one hole you get a particle or lump pattern at the detection screen. Open both holes and you get a wave (interference) pattern at the screen.

But if you shine light on the electrons at the two holes (as they say: to detect the particles) the pattern at the screen changes back to the particle or lump pattern. This time with two lumps directly behind the holes.

The Observer Created Reality interpretation of this last situation by Quantum Mechanics is that by looking at the electrons(measuring them) we have made them particles instead of waves. But particles are always particles as we see them in bubble chambers. Einstein hated Observer Created Reality more than anything else in Quantum Mechanics. And I am here to vindicate him.

What if there is a new phenomenon where light interacting with the electrons at the holes collapses their wave function? If this is true then for a very small amount of time the particles are waveless. Sometimes there is no wave! There is no wave for the electron when light interacts with it (called scattering.)

There is no wave for the electron for it to cause the wave interference effect at the detection screen. By adding light you collapse the wave function of the free electrons at the holes producing the particle pattern(two lumps behind the holes) again.

I have found at least one place where the wave function collapses.

Einstein? You were right!!! No Observer Created Reality

As waves probability waves must grow to size and in the wave function collapse they must shrink. They shrink to point particles. I say that's how particles become waveless.

If you've been able to follow hope you like this! :!!)

2. Nov 14, 2005

### vanesch

Staff Emeritus
Yes, but you have not shown any "wave collapse" here. Try to explain delayed quantum erasure experiments that way...

3. Nov 14, 2005

### ZapperZ

Staff Emeritus
You have a seriously faulty understanding of QM, the very thing that you want to analyze. I suggest you look at Marcella's treatment (do a search on here) of slit interference effects from a purely QM treatment without having to invoke these "wave" and "particle" picture which are purely CLASSICAL! The "switching" between particle and wave picture is NOT QM. It is OUR classical insistance that particle and wave behavior are separate things. QM has no such distinction!

You also seem to have completely ignored the fact that the interference effects arose out of the superposition of PATHS that these things can take. Such superposition is destroyed as soon as you try to do your light gymnastics.

Zz.

4. Nov 14, 2005

### Careful

How would you be able to determine the number of particles in your theory, and as such the dimension of configuration space on which the fictitious Schroedinger wave lives, if you cannot speak about the reality of the particle concept to start with?? On the contrary, QM needs the classical concept of particle (and measurement) in order to link to (if you want to: observer dependent) reality ! Bohr, Heisenberg and many others were very much aware of this.

5. Nov 14, 2005

### vanesch

Staff Emeritus
Of course the "particle" concept is used in (non-relativistic) quantum theory, but it is not the "bullet particle" with all its properties from classical physics ; essentially in classical physics, the bullet particle is a *position* in space as a function of time (a worldline), to which we associate mass and eventually some other quantities. In QM only the mass and other properties remain, and it becomes only the "bullet particle" when you explicitly prefer the position basis. But the very use of the position basis as a defining base of the Hilbert space of states is the remnant from this classical "bullet" particle.

6. Nov 14, 2005

### ZapperZ

Staff Emeritus
Where exactly in my posting that you quoted that indicates that I am pushing the "particle concept to start with"?

Zz.

7. Nov 14, 2005

### Careful

Did I say anything about bullet like or point particles? All I did was reacting to the sentence of ZapperZ : It is OUR classical insistance that particle and wave behavior are separate things. QM has no such distinction!´´ which is not correct, by the very definition of measurement itself. Moreover, it is obvious that measurement is not going to be associated with a distributional (ideal) position state, but rather with the state associated to a characteristic function determined by a domain in space of radius around 10^{-12} meters (ZapperZ is an experimentalist, so perhaps he can tell me if this accuracy is already higher in these days). Moreover, we both know that it is notoriously difficult (and an unsolved problem) to define a suitable particle notion for a quantum field (and doing so smells like attaching a reality to the quantum field - if the particle were not to be pointlike). Concerning the rolling of the muscles by Macro, I can only regret this as much as I regret the Schwartznegger quotient of some other quantum physicists here.

Cheers,

Careful

8. Nov 14, 2005

### ZapperZ

Staff Emeritus
Can you show me explicitly where in QM that such a distinction is made? In Marcella's painful derivation of the interference effects from single, double, and multi-slit experiments, not even once was there any need to invoke "wave" or "particle" picture. Perhaps you should look at that and point to me where QM does such a thing rather than giving an esoteric answer such as "definition of measurement".

I'd love to say more especially on Tony Leggett's point regarding the "measurement problem", but I'm catching a plane, and I don't run as fast to go after it.

Zz.

9. Nov 14, 2005

### Careful

There is nothing esoteric about the measurement aspect in QM. I do not need to see this derivation to know that *for these interference purposes* you only need the Schroedinger wave (but that was not the point). I am not interested in anyone's point of view on the measurement problem (have discussed enough about it with those who have researched on it for many years) unless he or she offers a solution for it. Have a good flight.

Cheers,

Careful

Last edited: Nov 14, 2005
10. Nov 14, 2005

### tbone

Not to break up the lengthy argument, but referring to the original question, I always understood that it's not where the fave function collapses but when, which would take you back to when is a measurement actually made. Thoughts?

11. Nov 15, 2005

### raphaelzorgue

We published an experimental result which goes in the direction of a geometrical interpretation of quantum mechanic: there is a particle and there is a wave. This result shows that a particle (electron in our case) has an internal clock frequency in its rest frame nu0=m0c2/h, as conjectured by Louis de Broglie as early as 1924. The paper was published in the “Annales de la Fondation Louis de Broglie” in october 2005 (vol 30 n°1page 109). It can be read on the AFLB site “http://www.ensmp.fr/aflb/AFLB-301/table301.htm” or on my site “http://www.freewebs.com/raphaelzorgue”

12. Nov 15, 2005

### Careful

Ah, but in relativistic physics this is not that easy. Where reffers then to where in space time?

13. Nov 15, 2005

### Macro

Sometimes there is no wave!!! :!!)

14. Nov 15, 2005

### tbone

good point careful, i hadn't thought of that

15. Nov 17, 2005

### raphaelzorgue

16. Nov 18, 2005

### kleinwolf

Study of QM measurement

Since the quantum description is known, for example a qubit : $$\Psi=\Psi(\phi)$$..then one could start the collapse during the measurement by an a posteriori or phenomenological approach with statistics over experimental results : hence the formalism should give the results : $$p_{out}=p(\phi,n)$$...where n indicates the measurement number....or for more precise exercises : $$n=n(x,t,\lambda)$$

Then the duty is to find a theory involving the additional parameters....in some way...

17. Nov 28, 2005

### Macro

Why would light cause waves to not interfere?

18. Nov 29, 2005

### cygnus2

yeah, i dont think ur explanation is right. u do not need to think of paticles and waves sepatately like this! this can be extremely confusing at times. paticles can interfere as easily.maybe u can refer to feyman's QED for a really wonderful exposition of these ideas.

19. Nov 30, 2005

### Macro

I made my point. Sometimes there are no waves. They collapse; thus no wave interference. Sometimes a particle is just a particle. For how long is the question quantum mechanics needs to answer.

20. Dec 2, 2005

### Longstreet

I think the confusion is that even when you shine light at the slits, you could really only consider the wave-function to be collapsed for an instant. From the point of the slit to the screen it acts as a wave again. You could see it if you put a second slit that doesn't have light on it between your first slit and the screen. The first slit simply acts as a source now.