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Schrodinger's cat new Cheshire grin
August 26, 2013 12:39 PM   Subscribe

Physicist Art Hobson disentangles 'Schrodinger's cat' debate. The solution is within the framework of standard quantum physics. 'In an article published August 8 by Physical Review A, a journal of the American Physical Society, Hobson argues that the phenomenon known as "nonlocality" is key to understanding the measurement problem illustrated by "Schrodinger's cat."'
posted by VikingSword (29 comments total) 8 users marked this as a favorite

 
Check the room, cat is not in it. Get up to lock the door, turn around, cat is now on the bed. You can't explain that. No one can. Not Schrödinger, and not this guy.

(eagerly awaiting for the MePhi Physics Phorce to arrive on the scene and explain the articles above)

posted by jquinby at 12:44 PM on August 26, 2013 [5 favorites]


Check the room, cat is not in it. Get up to lock the door, turn around, cat is now on the bed. You can't explain that. No one can. Not Schrödinger, and not this guy.
There is a nonzero probability that some of the energy in the room spontaneously arranged itself into a cat when your back was turned.
posted by Flunkie at 12:54 PM on August 26, 2013 [2 favorites]


Well, crap. There go all my Schrodinger's cat jokes.
posted by NedKoppel at 1:03 PM on August 26, 2013


Hobson argues that the phenomenon known as "nonlocality" is key to understanding the measurement problem illustrated by "Schrodinger's cat."

Does he mean "nonLOLCATity"? Otherwise I don't really understand this.
posted by Kabanos at 1:06 PM on August 26, 2013 [10 favorites]


Man, I love/hate popular theoretical physics articles. They're super entertaining, but you waste 15 minutes reading the whole damn thing, just barely understanding stuff enough to form a picture and sort of follow along, but leave no smarter than when you entered.
posted by resurrexit at 1:08 PM on August 26, 2013 [1 favorite]


Hi guys, just arrived at a workshop today and so am a little busy. If I have time, I'll come back here later and talk more about this, but this is an issue with a long history and so it requires careful thought. Which is to say, I can't drop bullshit like I usually do.

I see the linked article is behind a paywall and the pop-sci version read like a load of nonsense to me. I don't see an article with the exact same name on arXiv, but Hobson has 3 articles addressing similar issues. These articles are public and free for all. The links to them are:
http://arxiv.org/abs/1206.5189
http://arxiv.org/abs/1301.1673
http://arxiv.org/abs/1308.4055

There will be a quiz when I get back. I expect everyone to have done their homework.
posted by physicsmatt at 1:11 PM on August 26, 2013 [10 favorites]


I don't get how this does away with the Schrodinger's cat problem. We still don't know if the cat is alive or dead until there is observation, right? You can send your entangled particles through the "kill the cat/don't kill the cat" switch and continue to treat them as entangled particles. And until such time as you observe either the cat or one of the particles the cat is, theoretically, in a superposition of life and death, no?

Also, "nonlocality" is an anagram of "Lo! Yon Cat nil." That must, surely, be significant?
posted by yoink at 1:11 PM on August 26, 2013 [6 favorites]


IANAP, but I think there are good reasons not to throw away locality, it's a bit of a deeper property than it seems. For a local explanation of entanglement, see this rather older article.
posted by pixelrevolt at 1:12 PM on August 26, 2013


To demolish the cherished paradoxical precept of Schrodinger's Cat or to write a bunch of stuff I don't understand, that was Hobson's choice.
posted by Mister_A at 1:12 PM on August 26, 2013 [2 favorites]


This is essentially quantum entanglement applied to cats
posted by fallingbadgers at 1:15 PM on August 26, 2013


Lying bastards.
posted by Space_Lady at 1:16 PM on August 26, 2013


You can't explain that. No one can.

In our house, it's because there's a wormhole under the bed. We believe it leads to a spot behind the couch in the living room. Fucking wormholes, how do they work?
posted by rtha at 1:19 PM on August 26, 2013 [5 favorites]


Does he mean "nonLOLCATity"? Otherwise I don't really understand this.

I WAS IN A QUANTUM SUPERPOSITION ONCE.
IT WAS AWFUL.
posted by Strange Interlude at 1:22 PM on August 26, 2013 [3 favorites]


All this talk of quantum feline physics is neither here nor there; it is simultaneously here AND there.
posted by Mister_A at 1:30 PM on August 26, 2013 [3 favorites]


The Phys Rev A paper [Hobson, A. Two-photon interferometry and quantum state collapse. Phys. Rev. A 88, 022105 (2013)] appears to be the second of the ones physicsmatt linked:
http://arxiv.org/abs/1301.1673
And although I have not yet read it, I will say very judgmentally that I am troubled by the fact that it wasn't LaTeX'ed.
posted by Westringia F. at 1:32 PM on August 26, 2013 [2 favorites]


I am troubled by the fact that it wasn't LaTeX'ed.

You mean by that, of course, that he failed to invoke the "I'm rubber, you're glue" argument. That troubled me, too.
posted by yoink at 1:36 PM on August 26, 2013 [2 favorites]


As is almost always the case with trying to come up with an interpretation of quantum mechanics, this does not appear to offer any new predictions, but alternate explanation for what is "really happening."

In order to get around the superposition problem, Hobson has elected to invoke non-locality. This means he can say the cat is never in two mutually exclusive states. But I suspect in exchange for being able to say that, there will be scenarios where he has to say the cat's fate was literally decided retroactively by how you perform the measurement.

http://arstechnica.com/science/2012/04/decision-to-entangle-effects-results-of-measurements-taken-beforehand/

I believe quantum mechanics is fundamentally weird, you just have to decide for yourself which weirdness is the most plausible: time travel, observation influences reality, multiple realities, etc.
posted by justkevin at 1:37 PM on August 26, 2013 [5 favorites]


Not to mention, yoink, that I also grepped it and didn't find a single "QEDMF!" (I was speaking tongue-in-cheek earlier, in case that wasn't clear.)
posted by Westringia F. at 1:41 PM on August 26, 2013


> As is almost always the case with trying to come up with an interpretation of quantum mechanics, this does not appear to offer any new predictions, but alternate explanation for what is "really happening."

Exactly this! We have a theory (QM) that yields testable predictions about the things we can observe, and -- so far -- the theory works. The trouble with the ``measurement problem'' is that it necessarily considers things we cannot observe, which makes it rather difficult to come up with a falsifiable scientific hypothesis.
posted by Westringia F. at 1:56 PM on August 26, 2013


Strange Interlude: "Does he mean "nonLOLCATity"? Otherwise I don't really understand this.

I WAS IN A QUANTUM SUPERPOSITION ONCE.
IT WAS AWFUL.
"

----------

That's nothing. I was in a quantum supersuperposition once.

It was both awful and not awful.
posted by symbioid at 2:00 PM on August 26, 2013 [2 favorites]


Is this something I would need to observe in order to know whether or not I understand?
posted by Westringia F. at 2:03 PM on August 26, 2013 [3 favorites]


We call that consciousness, Westringia F.
posted by symbioid at 2:07 PM on August 26, 2013


Well, I thought I had finally got my mind wrapped around superposition. The theory I liked the most was that you could only have entanglement at a distance as long as neither particle interacted with some other random particle. This meant that macro objects would be essentially impossible to become entangled because there's too much interaction with other particles. So in the Schroedinger's cat case, a stray bump from an oxygen atom and boom, the wave function collapses.

To be more precise about it, as long as no information leaks from the entangled system, it remains in superposition, but if any information leaks, then it collapses as the information will describe what the actual state would be. So in the example above, that stray oxygen atom either bumps into superposition cat, and bounces away a bit more energetically if the cat is alive, or a bit less so if the cat is dead.

Anyway, the way the article framed things is that the entangled cat was in a single state, not two, but I didn't understand why. I mean if the atom itself is in superposition, then why not the cat. And if the atom isn't, then how did the atom come to not be in superposition. Saying that the cat mirrors what happens to the atom seems a bit circular to me, but I admit I barely have a layman's grasp and hope a real Physicist can shed some light here.
posted by forforf at 3:31 PM on August 26, 2013


Also, "nonlocality" is an anagram of "Lo! Yon Cat nil." That must, surely, be significant?

As far as that goes, I think it's significant that attempting the Schrodinger's Cat experiment would almost certainly result in Scratched Groins.
posted by Wolfdog at 4:00 PM on August 26, 2013 [1 favorite]


the Schrodinger's Cat experiment would almost certainly result in Scratched Groins.

Or scratchier dongs.
posted by yoink at 4:04 PM on August 26, 2013


wasn't here another Hobson who came up with this, except with horses?
posted by lapolla at 4:07 PM on August 26, 2013 [1 favorite]


I kinda think that then collapse of the wave function is a quirk of human perception and is only caused by you, the observer, becoming entangled with the object being observed via the measurement device. There is never really a time when it 'collapses', everything is always in a superposition, including you.
posted by empath at 4:17 PM on August 26, 2013 [1 favorite]


Wow, flashback. At university I took undergrad Physics at the UofA back in the early 90s, and Art Hobson was the professor. He was pretty interesting as far as I can remember, but I more distinctly remember he came one night with his family to the movie theater I worked at and was extremely cranky (not knowing I was actually one of his students) because the Bargain Night price didn't apply to the new movie they were seeing. That was Hollywood's call, Professor Hobson, not mine!
posted by zardoz at 5:10 PM on August 26, 2013


Did you offer Hobson the choice of paying full freight or GTFO?
posted by Mister_A at 7:26 AM on August 27, 2013


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