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Old 2005-10-26, 05:50   #1
Peter Nelson
 
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Question Schrödinger's Cat

I was interested in Quantum Computing and did some reading which brought me to Quantum bits (qubits), quantum teleportation, and other ideas of quantum mechanics.

Of course a famous tale is the "thought experiment" proposed by Shrodinger where a cat is placed in a box.

Also in there is a radioactive nuclei (which has an equal chance of decaying or not within the hour), and a poison gas which will be released when (if) the nuclei decays.

Since the nuclei is said (by QM theory) to be simultaneously in decayed/undecayed state until OBSERVED to be one or the other, Schrodinger questions the implications of this.

He is saying that there can be no simultaneously Dead AND Alive cat - it is one or the other, regardless of us opening the box to look.

This is all well known (although many misunderstand him as saying the cat WAS simultaneously dead/alive).

However what has not been considered:

The experiment was conceived so there was equal ie 50% chance of the nuclei decaying during the time period before the cat was observed.

However, it seems to me that either:

a) the cat could still be alive because the nuclei is undecayed so no poison
b) the nuclei decayed and the poison killed the cat so it is dead

But also a THIRD option:

c) undecayed therefore no poison, BUT the cat died of natural causes, old age or starvation or suffocation.

If follows that the chances the cat is observed to be dead at the end of the experiment are GREATER than 50%.

Does this mean the cat is more dead than alive?

FURTHER,

let's say we do without the nuclei and the poison.

We just wait an hour (the experiment duration) then look into the box to see if we have a dead cat an hour later.

By experimental observation we find the cat is either dead or alive.

What state was the boxed cat now in before observation? Was it "mostly alive" because of the slim chance that it died of natural causes or starvation while boxed up? Would this not equally apply if we also do without the box?

If this applies to cats, can we generalise to include humans? And if so (because we will all die sometime, possibly within the next hour) can we be considered "mostly alive but partially dead" in a Quantum mechanics sense?

Comments?

Last fiddled with by Peter Nelson on 2005-10-26 at 05:58
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Old 2005-10-26, 12:18   #2
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No comments but a few pedantic quibbles. The name is spelt Schrödinger, though the umlaut is often skipped by those witout the extended ASCII character set or non-English speakers. Also nuclei is plural, nucleus is singular. </end pedantic mode>
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Old 2005-10-26, 18:29   #3
ewmayer
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The cat's not dead, it's resting... </python_monty>
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Old 2005-10-27, 07:11   #4
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On a more serious note, Schrodinger never claimed that the cat can be both alive and dead. This thought experiment was devised to illustrate that certain concepts in quantum mechanics cannot easily be transposed to the macroscopic level.

Last fiddled with by garo on 2005-10-27 at 07:16
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Old 2005-10-28, 16:47   #5
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The cat is catatonic. He had an apoplexy from the anticipation reflex, just couldn't stand waiting to see if a particle decayed to kill him.

I wonder if there is an opposide form to quantum entanglement. With entanglement, two particles effectively become linked twins such that what happens to one also happens to the other no matter how far apart they are. Is there such a state as quantum disassociation such that no matter how close together two particles are, they can't possibly interact? The inferences include a method of time travel. Just a bit of foolishness to go with the quantum cat.

Fusion
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Old 2005-10-28, 17:25   #6
R.D. Silverman
 
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Quote:
Originally Posted by ewmayer
The cat's not dead, it's resting... </python_monty>
No, he's pining for the fjords.
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Old 2005-10-28, 17:29   #7
garo
 
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Quote:
Originally Posted by R.D. Silverman
No, he's pining for the fjords.
E's not pining!! E's passed on. This cat is not more......'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisibile!! THIS IS AN EX-CAT.
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Old 2005-10-28, 17:34   #8
xilman
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Quote:
Originally Posted by Fusion_power
Is there such a state as quantum disassociation such that no matter how close together two particles are, they can't possibly interact? The inferences include a method of time travel. Just a bit of foolishness to go with the quantum cat.
Not as far as I know. Here's an argument which may (and, indeed, should) attract criticism from those who know far more physics than I do. ( are you reading this?)

If the particles have non-zero mass they will interact gravitationally, if nothing else.

To have no gravitational interaction, the particles must have zero-rest mass (such as a photon) and zero total mass --- meaning that they have infinite wavelength (presuming for the moment that this may be possible) which in turn implies that they particles are not localized at all and so can't be said to be "close together". Particles of zero rest mass, such as the photon, can be localized but then they have non-zero energy (and m = E/c^2) and so interact gravitationally.

Paul

Last fiddled with by xilman on 2005-10-28 at 17:35
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Old 2005-10-28, 17:38   #9
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Quote:
Originally Posted by R.D. Silverman
No, he's pining for the fjords.
I like that
but I admit that I had to consult Webster for pining

Last fiddled with by ppo on 2005-10-28 at 17:39
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Old 2005-10-28, 19:13   #10
ewmayer
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Quote:
Originally Posted by ppo
I like that
but I admit that I had to consult Webster for pining
Well, you're barkin' up the wrong pine tree there, mate - it's the glorious Oxford English Dictionary or nothin' for me. But then, you probably allus' wanted to be a lumberjack, anyway, am I right? (cue music for the lumberjack song)
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Old 2005-10-28, 19:21   #11
xilman
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Quote:
Originally Posted by ewmayer
Well, you're barkin' up the wrong pine tree there, mate - it's the glorious Oxford English Dictionary or nothin' for me. But then, you probably allus' wanted to be a lumberjack, anyway, am I right? (cue music for the lumberjack song)
You use the OED as a reference work and then commit the solecism of using "realise" instead of "realize"?

I'm shocked, I tell you, I'm shocked.


Paul
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