View Poll Results: To which interpretation of Quantum Mechanics do you subscribe?
Copenhagen 7 16.28%
Many-Worlds, a.k.a. Many-Histories, a.k.a. Relative State 11 25.58%
Many-Minds 0 0%
deBroglie/Bohm 7 16.28%
Other (which?) 15 34.88%
I don't know. 3 6.98%
Voters: 43. You may not vote on this poll

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Interpretation of Q.M.

by JamesOrland
Tags: interpretation
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JamesOrland
#1
Mar26-12, 06:41 PM
P: 93
I was wondering who/how many people in the forum subscribe to which interpretation, so I decided to make a poll :)

Also anyone is welcome to post content about each interpretation to illuminate people who may not know the difference and/or definition of an interpretation.
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JamesOrland
#2
Mar26-12, 06:55 PM
P: 93
By the way, to anyone who might not know or might have misconceptions about Many-Worlds, I recommend Max Tegmark's paper and this FAQ.
K^2
#3
Mar26-12, 07:42 PM
Sci Advisor
P: 2,470
I like Many-Worlds due to its elegance, but it is important to note that all interpretations are equivalent. Id est, actual predictions are exactly the same, and by definition, no experiment can be devised to distinguish between them. So if one interpretation is more convenient than another for a particular problem, there is no reason not to use it. A lot of basic measurement experiments are a lot easier to picture in Copenhagen, while anything to do with entanglement is usually much easier in Many-Worlds.

JamesOrland
#4
Mar26-12, 08:01 PM
P: 93
Interpretation of Q.M.

Quote Quote by K^2 View Post
I like Many-Worlds due to its elegance, but it is important to note that all interpretations are equivalent. Id est, actual predictions are exactly the same, and by definition, no experiment can be devised to distinguish between them. So if one interpretation is more convenient than another for a particular problem, there is no reason not to use it. A lot of basic measurement experiments are a lot easier to picture in Copenhagen, while anything to do with entanglement is usually much easier in Many-Worlds.
No, not by definition. I do believe both Hawking and Tegmark have suggested ways to distinguish between the different interpretations, and the fact that no tests have been made is no evidence that they never will (as I mentioned in another thread, one is reminded of Lord Kelvin's statement that the movement of muscles was infinitely beyond science).

That being said, the objective of the poll is to measure who agrees with what inside their heads, regardless of their calculations :)

--EDIT:

Actually, the FAQ that I posted above does mention a possible way to distinguish between Many-Worlds and Copenhagen, in Q37. It is a very interesting theory, I see promise in it.
K^2
#5
Mar26-12, 08:20 PM
Sci Advisor
P: 2,470
By definition, interpretations are part of the same theory. If there is distinction, they are distinct theories.

Under axioms of Quantum Mechanics, Copenhagen and Many-Worlds are interpretations. Id est, indistinguishable. While experiment could exist that would point towards one or another, it would simultaneously disprove Quantum Mechanics, as violation of one of the axioms is prerequisite for a distinction.
JamesOrland
#6
Mar26-12, 08:36 PM
P: 93
Quote Quote by K^2 View Post
By definition, interpretations are part of the same theory. If there is distinction, they are distinct theories.

Under axioms of Quantum Mechanics, Copenhagen and Many-Worlds are interpretations. Id est, indistinguishable. While experiment could exist that would point towards one or another, it would simultaneously disprove Quantum Mechanics, as violation of one of the axioms is prerequisite for a distinction.
Do elaborate on that. Let's take, for instance, the example discussed in Q37 of the FAQ I mentioned, the one about AI. How would it disprove Q.M. at the same time it disproved the Copenhagen interpretation?
Mark M
#7
Mar26-12, 08:43 PM
P: 526
Quote Quote by JamesOrland View Post
By the way, to anyone who might not know or might have misconceptions about Many-Worlds, I recommend Max Tegmark's paper and this FAQ.
I thought I'd also add Hugh Everett's dissertation that introduced MWI:

http://www.pbs.org/wgbh/nova/manywor...ssertation.pdf

It's funny that Quantum Mechanics is taught in terms of CI, but when it comes down to picking a side, you don't see too many people standing by it.

BTW, I went MWI. Also, great poll, thanks for posting this.
K^2
#8
Mar26-12, 08:59 PM
Sci Advisor
P: 2,470
Quote Quote by JamesOrland View Post
Do elaborate on that. Let's take, for instance, the example discussed in Q37 of the FAQ I mentioned, the one about AI. How would it disprove Q.M. at the same time it disproved the Copenhagen interpretation?
Look up Quantum Eraser which performs an experiment similar to the one described.
JamesOrland
#9
Mar26-12, 09:08 PM
P: 93
Quote Quote by K^2 View Post
Look up Quantum Eraser which performs an experiment similar to the one described.
That's beautiful. And... it does look to me like evidence against collapse postulates, in one way or another.
K^2
#10
Mar26-12, 09:22 PM
Sci Advisor
P: 2,470
Not exactly. It basically just says that collapse is relevant with respect to some "external observer". Same thing happens in Schrodinger's Cat experiment, after all. Cat's observations are considered irrelevant. This is still self-consistent so long as you consider only one observer. And there are actually some advantages of doing it this way. Decoherence, for example, can play a major role, and then it's actually convenient to distinguish between "true" observer, who read the measurements once decoherence took place, and intermediate observer, such as a measurement device that remained entangled to the measured state.

Point is, yes, it does get messy, and it is a big part of why I prefer MWI, but there is no actual contradiction that breaks Copenhagen. Just a lot of ugliness, which means that any time you rely on Copenhagen, you have to be extra careful with interpretation of results.
Hurkyl
#11
Mar26-12, 09:41 PM
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P: 16,099
I did vote for MWI, but I wanted to add two significant caveats:
  • The ideas of CI are still useful, but as inspiration for mathematical techniques. Interpreting CI within MWI (rather than as referring to reality directly) does a good job of patching up CI's flaws.
  • I expect deBB to turn out to be roughly equivalent to MWI, in a sense similar to how Lorentz Ether Theory is equivalent to Special Relativity.
JamesOrland
#12
Mar27-12, 01:36 PM
P: 93
Quote Quote by K^2 View Post
Not exactly. It basically just says that collapse is relevant with respect to some "external observer". Same thing happens in Schrodinger's Cat experiment, after all. Cat's observations are considered irrelevant. This is still self-consistent so long as you consider only one observer. And there are actually some advantages of doing it this way. Decoherence, for example, can play a major role, and then it's actually convenient to distinguish between "true" observer, who read the measurements once decoherence took place, and intermediate observer, such as a measurement device that remained entangled to the measured state.

Point is, yes, it does get messy, and it is a big part of why I prefer MWI, but there is no actual contradiction that breaks Copenhagen. Just a lot of ugliness, which means that any time you rely on Copenhagen, you have to be extra careful with interpretation of results.
I see. But this isn't exactly like the example I mentioned, because in the example I mentioned there is actual reversibility and not just the same irreversible process (release of pairs of entangled photons) repeated under different but related conditions. I am not sure that would make any difference, but intuitively to me it seems it might. Of course, as I myself mention a bit, human intuition isn't a reliable thing, so I talk to people who know more about the subject than I do and who can explain about it.

Whichever use we make, it is my belief that even if all interpretations are truly unprovable and/or indistinguishable, we should try to find the correct one, because matching my inner map with the territory is a terminal value to me (i.e. something I find to be desirable regardless of its practical utility). So even if there are no practical utilities, I strive to make my models of the world as accurate as possible within my limited framework and incomplete knowledge.
Delta Kilo
#13
Mar28-12, 05:37 AM
P: 271
Quote Quote by JamesOrland View Post
Actually, the FAQ that I posted above does mention a possible way to distinguish between Many-Worlds and Copenhagen, in Q37. It is a very interesting theory, I see promise in it.
With all due respect, the answer to Q37 is a collection of epic fails. It will prove nothing.
* Consciousness is not required for collapse in orthodox CI, only the act of measurement.
* Critics will just say AI is not a 'true consciousness' anyway.
* Reducing heat dissipation by itself will not make computations reversible.
* 'Reversible measurement' is oxymoron by definition.
* If the system is in contact with environment, it will not be able to reverse the measurement,
* if the system is isolated, it will not cause world split, just a local entanglement.
etc. etc.

A much better way to go would be to have a good comprehensive model of measurement process that would render collapse postulate totally superfluous. Decoherence certainly goes some way towards this goal.
JamesOrland
#14
Mar28-12, 07:21 AM
P: 93
Quote Quote by Delta Kilo View Post
With all due respect, the answer to Q37 is a collection of epic fails. It will prove nothing.
* Consciousness is not required for collapse in orthodox CI, only the act of measurement.
* Critics will just say AI is not a 'true consciousness' anyway.
* Reducing heat dissipation by itself will not make computations reversible.
* 'Reversible measurement' is oxymoron by definition.
* If the system is in contact with environment, it will not be able to reverse the measurement,
* if the system is isolated, it will not cause world split, just a local entanglement.
etc. etc.

A much better way to go would be to have a good comprehensive model of measurement process that would render collapse postulate totally superfluous. Decoherence certainly goes some way towards this goal.
Oh, I don't think the argument was based on the consciousness fact per se, just a reversible machine.

From what I understood, the experiment measures the data with a machine that simply holds it in a single bit, and then erases that bit regardless of what it was, effectively destroying any information of the measurement having been made, after it was made. According to a collapse postulate that doesn't need a conscious observer, once the measurement had been made the wavefunction should've been collapsed, regardless of anything else, just because there was a bit in a classical machine that changed from 0 to 1 because of the measurement.

Unless I misunderstood the experiment or the mathematics or I'm just being a victim of Confirmation Bias :P
Delta Kilo
#15
Mar28-12, 08:31 AM
P: 271
Quote Quote by JamesOrland View Post
Oh, I don't think the argument was based on the consciousness fact per se, just a reversible machine.
Well, why then do they talk about AI and a computer comparable in complexity to human brain? Ah, never mind.

Quote Quote by JamesOrland View Post
From what I understood, the experiment measures the data with a machine that simply holds it in a single bit, and then erases that bit regardless of what it was, effectively destroying any information of the measurement having been made, after it was made.
Well, they say:
The machine now reverses the entire x-axis measurement - which must be possible, since physics is effectively reversible, if we can describe the measuring process physically - including reversibly erasing its memory of the second measurement.
Well, that's just not going to work. In CI it is simply not possible period. In MWI it depends on how far the interactions are allowed to spread. If the interaction is confined to a small part of the system (eg. a single bit), it might be possible to reverse it but it wouldn't be a measurement, just an entanglement (the bit in memory will be in superposition). If the decoherence spreads to the whole system but not to its environment (system is isolated), then the system will not be able to undo the measurement and it might detect that the collapse has in fact happened. However, from the point of view of outside observer there will be two copies of the system in superposition. Now, depending on how this outside observer interacts with the system, with lots of of luck it might be able to detect this.
And finally, if the decoherence is allowed to escape into the environment, that's it, there will be two copies of the observer, each one seeing the apparent collapse happening.
moogull
#16
Mar28-12, 08:38 AM
P: 82
I like Many-Worlds, and this goes back to when I was in sixth grade I held this belief. After seeing the movie the Time Machine, I had a little theory that there were actually different realities all happening at the same time that we couldn't see, only our own. I also thought that these realities were not at the same time, which was different from Many-Worlds, but it allowed for time travel by jumping between these alternate realities at different times.
JamesOrland
#17
Mar28-12, 09:11 AM
P: 93
Quote Quote by Delta Kilo View Post
Well, that's just not going to work. In CI it is simply not possible period. In MWI it depends on how far the interactions are allowed to spread. If the interaction is confined to a small part of the system (eg. a single bit), it might be possible to reverse it but it wouldn't be a measurement, just an entanglement (the bit in memory will be in superposition). If the decoherence spreads to the whole system but not to its environment (system is isolated), then the system will not be able to undo the measurement and it might detect that the collapse has in fact happened. However, from the point of view of outside observer there will be two copies of the system in superposition. Now, depending on how this outside observer interacts with the system, with lots of of luck it might be able to detect this.
And finally, if the decoherence is allowed to escape into the environment, that's it, there will be two copies of the observer, each one seeing the apparent collapse happening.
That actually makes a lot of sense. Thanks for explaining it to me :)

Quote Quote by moogull View Post
I like Many-Worlds, and this goes back to when I was in sixth grade I held this belief. After seeing the movie the Time Machine, I had a little theory that there were actually different realities all happening at the same time that we couldn't see, only our own. I also thought that these realities were not at the same time, which was different from Many-Worlds, but it allowed for time travel by jumping between these alternate realities at different times.
I recommend you read this. Do it with a grain of salt, of course, as you should with everything you read (don't believe everything you're told, that is).

---

On another topic, I was wondering to which interpretation the people who voted for 'Other' subscribe :P
moogull
#18
Mar28-12, 10:57 AM
P: 82
I recommend you read this. Do it with a grain of salt, of course, as you should with everything you read (don't believe everything you're told, that is).
Thanks!


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