Re: Guest Post - schroedinger's rat

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The two-track editorial process for PNAS is something else. A terrible, terrible something else.


Posted by: Sifu Tweety | Link to this comment | 03- 4-14 2:57 PM
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Does anybody else pronounce PNAS as 'penis?'


Posted by: togolosh | Link to this comment | 03- 4-14 3:26 PM
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2: Does anybody not?


Posted by: essear | Link to this comment | 03- 4-14 3:55 PM
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Now I'm wondering which Unfoggeder works in quantum information.


Posted by: essear | Link to this comment | 03- 4-14 3:55 PM
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And what kind of pet they have.


Posted by: LizardBreath | Link to this comment | 03- 4-14 3:58 PM
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I'm stuck staring at the sentence "The problem is to explain why measurements return a single outcome, not why we don't see macroscopic superpositions." What does "return a single outcome" mean if it doesn't mean "we don't see macroscopic superpositions"? I don't understand quantum foundations people at all.


Posted by: essear | Link to this comment | 03- 4-14 4:08 PM
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4: Sshh!

5: My landlord doesn't allow pets.

6: I think "we don't see macroscopic superpositions" has two possible meanings: one is that "every measurement returns a single outcome," and the other is that "noise processes cause any macroscopic superposition state to rapidly collapse into a classical state." I think he's arguing that the second statement may have practical importance, but it doesn't shed any light on the first statement, which is the "foundational" question.


Posted by: president nixon | Link to this comment | 03- 4-14 5:08 PM
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But, yeah, quantum foundations is slippery stuff. It's an area of science that seems very aesthetically-driven. Very few of those papers identify a new phenomenon; mostly they just try to explain why quantum mechanics is the way it is, for instance by trying to derive quantum mechanics from some "deeper" principle (e.g., information causality). Which is a fine goal, although I am a bit pessimistic about the chances of success, as they have been trying to do this for most of a century. Alas it's very subjective, deciding what makes a good explanation. Which is how people get away with publishing such crazy shit.


Posted by: president nixon | Link to this comment | 03- 4-14 5:17 PM
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I read that book about the hippies and quantum physics. Turns out the hippies saved physics by being so embarrassingly wrong that the rest of physics was roused to shut them down.


Posted by: Sifu Tweety | Link to this comment | 03- 4-14 5:26 PM
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Without wanting to resurrect the "Niels Bohr had it a lot more right than he is ever given credit for wars" isn't the answer to the question in 6 really just something like "a measurement is just another name for a single outcome"? Thinking of measurements as special spooky ceremonial events, rather than as sums over histories is precisely how people confuse the shit out of themselves over the Copenhagen Interpretation


Posted by: dsquared | Link to this comment | 03- 4-14 5:31 PM
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I appreciate the placement of the second " in 10.


Posted by: Sifu Tweety | Link to this comment | 03- 4-14 5:33 PM
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Also, before this thread goes up to 200 comments about quantum foundations some random topic, I also like what the Rat has to say about working with experimentalists. I have to confess that I think experimentalists are cool, and wouldn't resist too much if one of them wanted to write an intellectually shallow paper with me, as long as it involved a mode-locked laser and some really fast electronics. But it's good to be reminded that this may not be the best use of our time.


Posted by: president nixon | Link to this comment | 03- 4-14 6:18 PM
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too clever didn't read


Posted by: JP Stormcrow | Link to this comment | 03- 4-14 6:31 PM
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I feel like in principle I should be interested in this blog but in practice it's incomprehensible to me. I'm kind of vaguely aware that there are experimentalists trying to test whether quantum mechanics works, but I don't entirely understand why. We have so many exquisitely precise experimental tests of it already and no theoretical reason to expect it would ever break down, since it seems to be a pretty rigid framework. As opposed to the situation in particle physics, where we have fairly good reasons to expect our theory to break down and the damn thing just won't break.


Posted by: essear | Link to this comment | 03- 4-14 8:20 PM
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Also I have to admit I still don't really understand 7.last. Macroscopic superpositions will decohere into classical-looking states, and observers get entangled with the thing they're observing. I'm not sure in what sense this is different from "measurements return a single outcome".

(Experience also shows I have very little patience for discussions of quantum foundations, and also for discussions in which dsquared talks about science, so I should probably stop here.)


Posted by: essear | Link to this comment | 03- 4-14 8:21 PM
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I feel like in principle I should be interested in this blog but in practice it's incomprehensible to me.

New mouseover text.


Posted by: Jesus McQueen | Link to this comment | 03- 4-14 8:21 PM
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Hee. I didn't mean this blog, of course.


Posted by: essear | Link to this comment | 03- 4-14 8:23 PM
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we have fairly good reasons to expect our theory to break down and the damn thing just won't break

Until ATTACKED BY DINOSAURS!


Posted by: Sifu Tweety | Link to this comment | 03- 4-14 8:24 PM
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observers get entangled with the thing they're observing

ATM

(sorry, one for old times' sake)


Posted by: Kreskin | Link to this comment | 03- 4-14 8:37 PM
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Probing the dark matter!


Posted by: | Link to this comment | 03- 4-14 8:39 PM
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14: Agreed, for most of these experimental tests of quantum mechanics, no one is expecting to be surprised.

We have so many exquisitely precise experimental tests of it already and no theoretical reason to expect it would ever break down,

On the other hand, there do seem to be a lot of people who believe that quantum mechanics works for natural systems, like in condensed matter physics, but that it somehow breaks down if you try to build a large-scale quantum computer. They usually blame this on decoherence, but it has to be a bit subtle, because simple kinds of noise don't actually prevent you from building a quantum computer (at least in theory).

And then there is the black hole information paradox, so we know something weird has to happen to either quantum mechanics or general relativity in that situation. That seems pretty compelling to me, although not experimentally testable. Also I don't know enough about it (but wish I did!).

15: Yeah, I think I can see why people are bothered by the "measurement problem," but I don't really know what kind of answer would make them feel better.


Posted by: pres. nixon | Link to this comment | 03- 4-14 8:55 PM
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Occasionally I'm sad that I pretty much can't follow the math and science threads. I guess I should have read C. P. Snow's novels.


Posted by: fake accent | Link to this comment | 03- 4-14 9:25 PM
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14: Thank you! I didn't make it very far down the page before it was just words words look at me I'm so smart words words. It makes me all insecure and grumbly.


Posted by: antipodestrian | Link to this comment | 03- 5-14 2:59 AM
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23: but this is the funniest thing that's happened in quantum information in ages! Arrgh, this means we're doing it all wrong, doesn't it...


Posted by: pres. nixon | Link to this comment | 03- 5-14 9:41 AM
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macroscopic superpositions

Belle Knox's best scene.


Posted by: Todd | Link to this comment | 03- 5-14 9:59 AM
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I have no idea what this guy is talking about but still enjoyed reading it. It reminds me a lot of when I read the entire archives of a blog about Norwegian soccer. Good writing, man.


Posted by: Cryptic ned | Link to this comment | 03- 5-14 10:10 AM
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