Does Observation Truly Collapse a Wave Function?

[QUANTUMQ]

i did ask the question "since two particles can be entangled, are the wave functions of these two particles entangled before they collapse? and is a wave function collapse perminent?" but it got lost in the philosophy discussion, so is there any answers on the original question?

 

[yasiru89]

i did ask the question "since two particles can be entangled, are the wave functions of these two particles entangled before they collapse? and is a wave function collapse perminent?" but it got lost in the philosophy discussion, so is there any answers on the original question?

This has ultimately come down to a matter of interpretation. The interaction/observation is what collapses a wave-function, but its quite true that, given an interaction is not observed the systems (we'll say particles for convenience) will entangle. Thus the matter comes down to what constitutes an observation. Of course, for all practical purposes, the Copenhagen interpretation circumvents this matter completely- but seeing as this is the philosophy discussion, I will take the liberty to introduce Eugene Wigner's thought experiment 'Wigner's friend', which raises, more bluntly than ever, the same problem Schroedinger's cat presents (though of course, both are irrelavent to the actual physical application of quantum theory). Wigner considers this as decisive that consciousness has a role to play in collapse.


See Eugene P. Wigner, Symmetries and Reflections: Scientific Essays (MIT Press, 1970)

 

[ThomasT]

what is it that actually collapses a wave function, an observer? what constitutes an observer? also is it true that everything has a wave function, because if it does who collapsed the universes wave function
some may say wave function collapse only works on the quantum level but the universe was sub atomic sive at the time of the BIG BANG.

can resistance in space-time also collapse wavefunctions

if a person collapses a wave function by looking (observing) where does light come into the question. for the person to actually make the observation the light has to travel from the wavefunction to tge persons eye, what if the light is intercepted by another persons eye.

also how can light wave function collapse?

The collapse of the wavefunction might be a misleading way of characterizing what happens when qualitative results are obtained, ie., when detections are irreversibly recorded, if wavefunction collapse is taken to mean that there's some qualitative knowledge of what's happening in some underlying quantum reality.

QM wavefunctions might correspond in some way to what's happening in the deep reality of quantum level processes, but there's no way to precisely ascertain that. And, according to one interpretation of quantum theory, the Copenhagen Interpretation, the existence of a fundamental quantum of action (the principle component of any flavor of the quantum theory) precludes our ever having any qualitative knowledge of a quantum scale reality that underlies instrumental behavior.

What is known is that QM wavefunctions are mathematical tools that describe the expected frequency distributions of the results of quantum experiments. These probability distributions, which associate certain values with certain possible instrumental behaviors, apply to specific experimental preparations, or classes of similar preparations, and describe, and have physical meaning only with regard to, the expected statistical distributions of large accumulations of individual trial results.

I don't know of any reports of any observations of any qm wavefunction ever collapsing.

On the other hand, we're in the philosophy forum so feel free to analogize qm wavefunctions with some sort of real wavelike disturbance -- like the ripples produced when you drop a stone into a calm pool of water. Put some obstacles/filters in the paths of the waves and see what happens.

Another cool thing to do is to put some sand or other finely particulate stuff on a drumhead and then set the drum to vibrating. Try different vibrational frequencies and see what sorts of standing wave patterns you can produce in the particulate stuff.

There are lots of simulations of wave behavior on the web. I don't have any links handy, but just Google stuff about waves and you should get some interesting hits.

 

[baywax]

why is there seemingly a lack of interest in the physics world into what subjectivity is when it seems to play a very important role?

I think physicists like to avoid subjectivity because subjectivity leads each individual to a separate conclusion with few instances where there is an agreement on a cause or an effect.

When numerical observations match-up there is little room for disagreement on a subjective basis since numbers are quantifiably the same in a mathematical and universal sense.

So, when I say something is blue, someone else will disagree and say its aqua. But if I give them the percentages of cyan, yellow, magenta and black there is no dispute regarding the value of the colour of a pigment. Same with light, if I give you the values and percentages of red, blue and green we can immediately agree on the quality of the colour of light.

 

[wawenspop]

This has ultimately come down to a matter of interpretation. The interaction/observation is what collapses a wave-function, but its quite true that, given an interaction is not observed the systems (we'll say particles for convenience) will entangle. Thus the matter comes down to what constitutes an observation. Of course, for all practical purposes, the Copenhagen interpretation circumvents this matter completely- but seeing as this is the philosophy discussion, I will take the liberty to introduce Eugene Wigner's thought experiment 'Wigner's friend', which raises, more bluntly than ever, the same problem Schroedinger's cat presents (though of course, both are irrelavent to the actual physical application of quantum theory). Wigner considers this as decisive that consciousness has a role to play in collapse.


See Eugene P. Wigner, Symmetries and Reflections: Scientific Essays (MIT Press, 1970)

The exact position of an electron (if that's the observable measured) is at the time of observation - ONLY.

The 'observer' was a terrible red herring brought about by the inability to comprehend superposition. So for example we had absurdities like 'how can a particle spin both ways at once' - Schrodingers cat is another absurd, historical example. The main line of the Copenhagen overcomes them.

Its not as if an electron suddenly becomes a tiny gray ball at a known position on decoherence. The electron remains a probablistic cloud - for want of a better description. Its position is only known exactly at the time of measurement, then its back to probabilities again - immediately.

 

[DaveC426913]

The 'observer' was a terrible red herring brought about by the inability to comprehend superposition. So for example we had absurdities like 'how can a particle spin both ways at once' - Schrodingers cat is another absurd, historical example. The main line of the Copenhagen overcomes them.

Are you saying that the concept of superposition eliminates the paradox of the Schrödinger's Cat thought experiment?

 

[wawenspop]

Are you saying that the concept of superposition eliminates the paradox of the Schrödinger's Cat thought experiment?

The cat was in the days when they were trying to hang on to electrons as particles rather than wave packets. You might say that a cat can spin two ways at once, that's absurd in the same way as dead and alive cats.

But if the cat were quantum sized, then sure 'it' can - because its a wave packet (probabilities) and no longer a little gray ball (or cat like thing).

I am not trying to be clever here. I assume we believe the main line of Copenhagen here and not MWI etc. I cannot see how you could accept the cat story at all.
Please make your point to prove me wrong!

 

[QUANTUMQ]

The exact position of an electron (if that's the observable measured) is at the time of observation - ONLY.

The 'observer' was a terrible red herring brought about by the inability to comprehend superposition. So for example we had absurdities like 'how can a particle spin both ways at once' - Schrodingers cat is another absurd, historical example. The main line of the Copenhagen overcomes them.

Its not as if an electron suddenly becomes a tiny gray ball at a known position on decoherence. The electron remains a probablistic cloud - for want of a better description. Its position is only known exactly at the time of measurement, then its back to probabilities again - immediately.

so is that to say that a wavefunction does not collapse, but just gives the appearence of a collapse

 

[wawenspop]

so is that to say that a wavefunction does not collapse, but just gives the appearence of a collapse

The wavefunction *realigns itself*, so if the first wave function had a probability (for say position), & then if that position were to be 'observed', then its position state would be a new probability after observation. Observation would be something like a collision with a photon or similar.

Imagine a violin string vibrating - then get a snapshot (which might change its phase) - then its still vibrating. i.e. it does not stop vibrating. -remember a violin string vibrating is only partially analogous to a wave function.