Schrödinger's cat must die!

woodguard said:
The particle that is observed, does it stay that same way forever or when my back is turned it jumps back into superposition?

Is the cat like the light in my fridge. When I open the door sometimes it’s alive and sometimes it is died.(If it is lives, does it like the tasted of brains?)
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This doesn't really apply to cats. Superpositioning only applies to subatomic particles. It cannot be scaled up to the macroscopic world.

What is meant by the observer? Would the cat kill itself (or free it’s self), if it seen the test equipment.
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Most QM researchers consider an 'observer' as, basically, anything that interacts with the particle - pretty much any matter in its environment could be considered to be the 'observer'.

Why does chemicals changing in a brain(the observer seeing something) collapses the wavefuction.
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It doesn't - 'observer' is a misleading term in this case (see above).

Is this one of those thing that looks real great on paper, but useless in real life? :blush:
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No, QM is extremely well tested and reliable as a theory. It affects just about everything in our universe. It is staggeringly complex (as would be any theory that describes the physical behaviour of subatomic particles in an object) but so far it seems to hold up as a theory.

You wouldn't necessarily want to use it to calculate what time a train leaving Baltimore at a certain speed would arrive in Chicago, but in theroy you could.
 
Can we put this into more accessable terms?

If I put a coin in a light tight box I can't see into, shake it up really well and then place the box on a flat surface (assuring that the coin is lying flat), am I more correct in saying that the coin is both heads and tails at the same time, or that it is either all heads or all tails and I just don't know which?

(I am of course referring to how a tossed coin is called -- all heads means heads side up, etc.)
 
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am I more correct in saying that the coin is both heads and tails at the same time, or that it is either all heads or all tails and I just don't know which?
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I LIKE cats, yes I do...

However, just because you can't see the darn coin does not make it both heads and tails. It is lying one way or the other, not spinning in the middle suspended in some kind of supernatural way.
 
I think the whole cat thing was actually supposed to show the ridiculousness of QM scaling up or something...
 
Correct me if I am wrong (seriously, I may be completely misremembering this) but isn't Schrodinger's cat related, in part, to Heisenberg's Uncertainty Principle?
 
Ashles said:
This doesn't really apply to cats. Superpositioning only applies to subatomic particles. It cannot be scaled up to the macroscopic world.
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Are you sure about this? My understanding was that at a macroscopic scale a definite state can be known without observance simply because the massive number of probabilistic entanglements between all of the particles gives us a standard error that approaches zero, and that there's not any inherent difference between sub-atomic and large scale objects.

Apparently fluids called Bose-Einstein Condensates exhibit quantum effects on a macro scale.
 
A similar QM question that maybe someone here can answer? I read in Scott Adam's book "The Dilbert Future" where he has a chapter on the Slit experiment and stuff like that, about a certain experiment. But it's not referenced and I can't find a reference to it anywhere.

If a measurement is made by computer (which would ordinarily collapse the wave or whatever you want to say to describe what happens) and the result it written to a hard disk, then the form collapses as normal.

But (and this is where my woo-alarm went off) if the measurement is made by the machine, but NOT recorded anywhere, then its as if the measurement wasn't made at all. And the particle remains in a wavelike state. Almost like, there's not enough "information" in the system to fill in all the details, so if we don't extract any hard info, then the details can remain fuzzy.

This seems crazy to me, (but so much of QM does). If true, a bunch of follow up experiments should have immediately occurred. e.g. What if the computer program was programmed to write randomised results?

So can anyone tell me? Was Scott talking out of his arse? Or is QM stranger again than I had ever imagined it was?
 
The cat would count as an observer, so this example is kinda silly.

Aside from that, the answer is both. It doesn't seem so absurd when the thing in two states at once is not sentient.
 
How about this ...

An observer takes note of the cat's condition and records the results -- collapsing the wave function. But, before he can tell anyone else, he dies and his results are destroyed (he was going to drive home with his notes but instead crashes and burns up ... everything). Did the wave function somehow collapse and then reform?
 
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It doesn't make any difference whether he is alive or not.
 
Ashles said:
This doesn't really apply to cats. Superpositioning only applies to subatomic particles. It cannot be scaled up to the macroscopic world.
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Most quantum researchers think its more a matter of money than something fundamental. Large molecules have been fired through double slit experiments, superconductos and BEC exhibit macroscopic quantum effects.

Most QM researchers consider an 'observer' as, basically, anything that interacts with the particle - pretty much any matter in its environment could be considered to be the 'observer'.
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Nonsense. For a start most researchers dont think about it at all. Of those that do, a small subset may well hope that some notion of decoherence solves the problem, but this always involves going beyond the standard formalism of quantum mechanics in one way or another, and most people are against that. Read an essay by Stephen Adler at the IAS "Why decoherence doesn't solve the measurement problem" for a simple overview. I just returned from an American Physical Society meeting which had a Special Focus Session for exactly this sort of stuff, attended by a high percentage of people who do work on it, and not one of them gave a talk remotely suggesting anything like what you said. Its simply a myth that floats around layman circles - and sadly a few circles of unthinking physicists too....
 
Just thinking said:
Do you mean the observer or the cat?

Plus, you really didn't answer my question.
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Well, Tez is obviously the guy to ask, because he's the expert.

He can correct me if I'm wrong, but, I meant the observer. It makes no difference if he dies. His death does not affect the collapse in any way.

So no, it did not collapse and reform.

Why would it?
 
Just thinking said:
How about this ...

An observer takes note of the cat's condition and records the results -- collapsing the wave function. But, before he can tell anyone else, he dies and his results are destroyed (he was going to drive home with his notes but instead crashes and burns up ... everything). Did the wave function somehow collapse and then reform?
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In that case it certainly doesnt reform! Another (more fortunate!) observer would describe the system by what is known as a mixed state - basically corresponding to his uncertainty about what the first observer recorded. Different observers can describe the same system with different quantum states according to their information about its preparation and/or subsequent interactions. There are strict consistency conditions on such multifarious descriptions of course!
 
Tez,

Just to clarify, so the various mixed quantum states are more reflective of our knowledge of the state of a system (and the possible knowledge), than the actual state of the system? (although actual state is meaningless, as it cannot be verified to be different from what we can determine from our knowledge fo the state. Hopefully I'm making sense).
 
Humphreys said:
Well, Tez is obviously the guy to ask, because he's the expert.

He can correct me if I'm wrong, but, I meant the observer. It makes no difference if he dies. His death does not affect the collapse in any way.

So no, it did not collapse and reform.

Why would it?
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The wave function would initially collapse upon the first observer's noting and recording the cat's condition (alive/dead). But if that information is never sent beyond his own knowing, to another observer this would constitute the first observer and cat as being within a 'bigger box' -- of which our second observer is not privy. Hence, to him, the wave function has not collapsed, until he somehow figures out what happened -- if he ever can.
 
Huntsman said:
Tez,

Just to clarify, so the various mixed quantum states are more reflective of our knowledge of the state of a system (and the possible knowledge), than the actual state of the system? (although actual state is meaningless, as it cannot be verified to be different from what we can determine from our knowledge fo the state. Hopefully I'm making sense).
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Its often the easiest way of thinking about it, especially in the multiple observer scenarios - you wont make a mistake that way. The math is just the math however, and within the formalism there is no way to prove that the quantum state is epistemic - there are many people (with accompanying interpretations) who treat it as having some sort of ontological status. [My suspicion is when things get complicated they revert to this "state of knowledge" viewpoint whether they realise and admit it or not!] The arguments in favour of viewing quantum states epistemically generally involve taking some other physical theory containing epistemic objects (such as Liouville mechanics) and pointing out all the analogies with quantum mechanics. This is not really satisfactory. What we'd really like is something where we can say "Look, quantum mechanics is clearly the theory of incomplete knowledge about [insert favourite pernicious leprechauns here] " - much like classical thermodynamics can be viewed as a theory of constrained knowledge about the atoms we couldn't originally "see"... This latter is my personal bias of course.
 
Correct me if I'm wrong, but wasn't the 'Schrodinger's cat" thought experiment a joke? Wasn't his intent to point out the ridiculousness of this very discussion?
 
blutoski said:
It's in one state or the other, but we don't know until we observe. To represent this in an equation, we need to add the two states' wavefunctions.
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Which means that it isn't in one state or the other.

When you add two wavefunctions, the resulting wave function is the sum of the two wave functions, not one or the other, either oscillating in time or...well I don't know how else to describe it.
 
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