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(Science Daily)   A physicist may have figured out if that damned cat is alive or dead. Or maybe not   (sciencedaily.com) divider line 77
    More: Interesting, Schrodinger, caterpillars, quantum superposition, quantum physics, physical review, quantum states, American Physical Society, University of Arkansas  
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4141 clicks; posted to Geek » on 26 Aug 2013 at 6:02 PM (51 weeks ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2013-08-26 06:14:05 PM
The cat is definitely alive.
 
2013-08-26 06:17:15 PM
Well, MY cat is alive. So it's all good.
 
2013-08-26 06:27:29 PM
"It is my hope that this resolution of the measurement problem will now be accepted by the quantum foundations community."

I hope his paper is better written than the article because it doesn't sound like he's resolved anything.

There is no logical connection made between
1) The cat and atom's states are entangled.
and
2) Therefore the cat does not exist in a superposition of states until observed
 
2013-08-26 06:31:13 PM

ParanoidAgnostic: "It is my hope that this resolution of the measurement problem will now be accepted by the quantum foundations community."

I hope his paper is better written than the article because it doesn't sound like he's resolved anything.

There is no logical connection made between
1) The cat and atom's states are entangled.
and
2) Therefore the cat does not exist in a superposition of states until observed


The Geiger counter is entangled with the particle ?!

The fact that two particles that are entangled does not change the fact that when you measure one both particles wave functions collapse, all this means is that you have two cats that are either alive or dead when you open the box.

/Still a long way from my GED in phyics
 
2013-08-26 06:32:10 PM
It's really easy to know if the cat is alive or dead -- you look in the damn box.
 
2013-08-26 06:39:12 PM

Donnchadha: It's really easy to know if the cat is alive or dead -- you look in the damn box.




THAT IS NOT ALLOWED!!
 
2013-08-26 06:39:13 PM
I have to say that I like Dr. Hobson's approach.  He attempts to teach quantum physics without paradoxes by suggesting that it's the nature of our assumption of what a particle is that leads to the paradoxes, but if we, instead think of the fields as fundamental and the particles as the fuzzier concept - a localized exchange of information about what's happening in the field - the the paradoxes resolve themselves.

I'm not sure I agree, completely, as, I think that non-locality IS strange.  He may have gotten rid of the paradoxes, but not the oddity.
 
2013-08-26 06:39:18 PM
The cat is dead.  Don't be an asshole.
 
2013-08-26 06:42:15 PM

kahnzo: I'm not sure I agree, completely, as, I think that non-locality IS strange.


I think you mean awesome.

It breaks faster than light travel. Two points in different places can share information simultaneously.
 
2013-08-26 06:47:37 PM
I'm really tired of hearing about that cat and, frankly, I don't care if it's alive or dead. What I want to know is, where is my FTL internet connection, Mr. Quantum scientist dude.

Oh, and would it kill you guys make a cheap, self-locating TV remote control?  How about entangling my remote control to the coffee table.
 
2013-08-26 06:48:38 PM

kahnzo: but if we, instead think of the fields as fundamental and the particles as the fuzzier concept - a localized exchange of information about what's happening in the field - the the paradoxes resolve themselves.


All paradoxes resolve if I wave my hands and say, "There are no paradoxes!" There is even a term for this is psychology and it is called "magical thinking".

justtray: It breaks faster than light travel. Two points in different places can share information simultaneously.


When you teleport me, I'll believe you. Until then, it is all just hand waving.
 
2013-08-26 06:48:54 PM
The cat is either outside or in my living room. However, based on the "article" this doesn't seem to really resolve anything.
 
2013-08-26 06:50:05 PM
I don't know why this took so long. It's a perfectly simple equation...

www.nothingaboutpotatoes.co.uk

Link
 
2013-08-26 06:54:00 PM

justtray: kahnzo: I'm not sure I agree, completely, as, I think that non-locality IS strange.

I think you mean awesome.

It breaks faster than light travel. Two points in different places can share information simultaneously.


From another paper by Dr. Hobson.  I tell Anita, on Venus, and Bernard, on Mars, that I'm sending one of them a turkey and the other a duck.  Anita gets a duck and instantly knows that Bernard got a turkey.  Bernard eats the turkey with mashed potatoes, sweet potatoes, and cranberry sauce.
 
2013-08-26 07:00:34 PM

worlddan: When you teleport me, I'll believe you. Until then, it is all just hand waving.


Lol, really? That's your requirement?

I'm afraid there's almost no chance you will live long enough to see that. Teleporting pieces of information is much easier than teleporting trillions upon trillions of pieces of information.
 
2013-08-26 07:01:13 PM

kahnzo: justtray: kahnzo: I'm not sure I agree, completely, as, I think that non-locality IS strange.

I think you mean awesome.

It breaks faster than light travel. Two points in different places can share information simultaneously.

From another paper by Dr. Hobson.  I tell Anita, on Venus, and Bernard, on Mars, that I'm sending one of them a turkey and the other a duck.  Anita gets a duck and instantly knows that Bernard got a turkey.  Bernard eats the turkey with mashed potatoes, sweet potatoes, and cranberry sauce.


Anita *assumes* Bernard got the turkey. It could have been eaten by the delivery driver.
Non-local information sharing makes no assumptions.
 
2013-08-26 07:02:10 PM

kahnzo: I have to say that I like Dr. Hobson's approach.  He attempts to teach quantum physics without paradoxes by suggesting that it's the nature of our assumption of what a particle is that leads to the paradoxes, but if we, instead think of the fields as fundamental and the particles as the fuzzier concept - a localized exchange of information about what's happening in the field - the the paradoxes resolve themselves.

I'm not sure I agree, completely, as, I think that non-locality IS strange.  He may have gotten rid of the paradoxes, but not the oddity.


How is what you described different from the Copenhagen interpretation?
 
2013-08-26 07:05:54 PM

kahnzo: From another paper by Dr. Hobson. I tell Anita, on Venus, and Bernard, on Mars, that I'm sending one of them a turkey and the other a duck. Anita gets a duck and instantly knows that Bernard got a turkey. Bernard eats the turkey with mashed potatoes, sweet potatoes, and cranberry sauce.


If they're entangled, then whether Bernard gets a raw or a cooked turkey would depend on whether or not Anita put her duck in the oven. The whole point of 'spooky action at a distance' is that you can do things to one member of the entangled pair when it is received (such as measuring its polarization along a particular axis) which instantly affect the other member.
 
2013-08-26 07:11:43 PM
I agree with the hand wavy aspect of the article and some of Dr. Hobson's papers.  I think he's basically saying that because we think of particles as very small billiard balls instead of manifestation of field interactions, our minds misinterpret what's "really going on."  Very hand wavy, but interesting anyway.I believe that Ted Chiang had a short story that developed this idea, but I can't remember what it was called.
 
2013-08-26 07:15:40 PM

Ivo Shandor: If they're entangled, then whether Bernard gets a raw or a cooked turkey would depend on whether or not Anita put her duck in the oven. The whole point of 'spooky action at a distance' is that you can do things to one member of the entangled pair when it is received (such as measuring its polarization along a particular axis) which instantly affect the other member.


So this is where I'm confused.  I've been on this physics kick lately (although I'm no student of it) and I've read that FTL communication is not possible because, while particles are entangled, all you can glean from one is the state of the other. (If you know Bob always wears one red sock and one green sock, and you see his left sock is red, you instantly know the right one is green. No real information transmitted)

But I thought I've also read that an entangled particle can be manipulated -- you can change the spin, for example -- and the other particle will follow suit instantly.  Does this not imply FTL communication?  Could you not devise an apparatus that communicates intentional changes to a particle's state?

What am I missing?
 
2013-08-26 07:17:13 PM

lifeboat: But I thought I've also read that an entangled particle can be manipulated -- you can change the spin, for example -- and the other particle will follow suit instantly.


This is false.
 
2013-08-26 07:18:51 PM

justtray: kahnzo: I'm not sure I agree, completely, as, I think that non-locality IS strange.

I think you mean awesome.

It breaks faster than light travel. Two points in different places can share information simultaneously.


No it doesn't.

You can't use non-locality/entangled particles to transmit information.

Think of it this way:

Say I have two quantum-entangled cats in two different boxes, set so that if I measure mine as dead, the other is alive.

Now say I open my box, and discover, lo and behold, my cat is alive. That means the other cat, even if it's on the other side of the universe, is dead. But here's the trick:

If I then KILL the cat in front of me, *THAT DOES NOT BRING THE OTHER CAT BACK TO LIFE*.

Entanglement goes away the moment you actually *measure* things. And no, if I drop the box into an incenerator before opening, that's still interacting with it, so the wavefunction has collapsed.

Ivo Shandor: If they're entangled, then whether Bernard gets a raw or a cooked turkey would depend on whether or not Anita put her duck in the oven. The whole point of 'spooky action at a distance' is that you can do things to one member of the entangled pair when it is received (such as measuring its polarization along a particular axis) which instantly affect the other member.


No. That's how Sci-fi explains entanglement. That's not actually what entanglement is.
 
2013-08-26 07:21:15 PM
You can decide which axis to measure which locks in the other particles information along that axis.  But you cannot "change the spin."  It's a bit subtle.
 
2013-08-26 07:22:55 PM

lifeboat: But I thought I've also read that an entangled particle can be manipulated -- you can change the spin, for example -- and the other particle will follow suit instantly. Does this not imply FTL communication? Could you not devise an apparatus that communicates intentional changes to a particle's state?


This is the part that's wrong. This *IS* how it works in sci-fi.. but, as it turns out, this isn't how it works out in reality.

This is where a lot of the confusion comes from.
 
2013-08-26 07:23:37 PM
This thread is making me hungry.  And given me an urge to join the ASPCA.
 
2013-08-26 07:25:37 PM
Ivo's "cooked or raw" state is analogous to choosing an axis, but he forgot to mention that there's a chance that Anita's duck isn't cooked even though she put it in the oven.  Not a good analogy.
 
2013-08-26 07:29:04 PM
lifeboat: (If you know Bob always wears one red sock and one green sock, and you see his left sock is red, you instantly know the right one is green. No real information transmitted)

But I thought I've also read that an entangled particle can be manipulated -- you can change the spin, for example -- and the other particle will follow suit instantly.  Does this not imply FTL communication?  Could you not devise an apparatus that communicates intentional changes to a particle's state?

What am I missing?


The measurement itself is a certain kind of manipulation, it disentangles the remote particle from the nearby particle and from a global perspective the state of the remote particle will be determined. However if we are forced to only look at the remote particle than we have no way of detecting these events.
 
2013-08-26 07:29:09 PM
Memo to everybody: if your supposed explanation of Schrodinger's thought experiment includes something called a "measurement" (or an "observation"), it's already wrong. And if it includes "wave function collapse", it's doubly wrong.

None of these things has any definition or description in quantum theory, they are just useful approximations for describing what is happening in most practical circumstances. But you can't use them to probe the foundations of QM; that requires you to be precise.
 
2013-08-26 07:32:07 PM
The Ted Chiang story I was thinking of is actually the main story in "Story of Your Life."

Worth a read, Felgraf.
 
2013-08-26 07:35:14 PM

kahnzo: Ivo's "cooked or raw" state is analogous to choosing an axis, but he forgot to mention that there's a chance that Anita's duck isn't cooked even though she put it in the oven.  Not a good analogy.


I agree, but I couldn't come up with a better one while staying within the theme of interplanetary poultry distribution. Sorry.
 
2013-08-26 07:37:00 PM
Ah.  Many thanks, all, for the clarification.
 
2013-08-26 07:44:05 PM

czetie: Memo to everybody: if your supposed explanation of Schrodinger's thought experiment includes something called a "measurement" (or an "observation"), it's already wrong. And if it includes "wave function collapse", it's doubly wrong.

None of these things has any definition or description in quantum theory, they are just useful approximations for describing what is happening in most practical circumstances. But you can't use them to probe the foundations of QM; that requires you to be precise.


So what's your preference?  Ensemble? Transactional? Many Worlds?  Consistent Histories?
You can't say "You can't do that!" and then lift your skinny fists like tiny antennas to heaven.

The problem doesn't go away because we can do things with more precision.  In fact, violations of Bell's Inequality are quite beautifully astounding, but in no way offer a satisfying resolution to the underlying weirdness.
 
2013-08-26 07:50:19 PM

albatros183: The Geiger counter is entangled with the particle ?!

The fact that two particles that are entangled does not change the fact that when you measure one both particles wave functions collapse, all this means is that you have two cats that are either alive or dead when you open the box.


My Physics is so rusty that I can't even tell if you're agreeing or disagreeing with me. I'll just assume that you're a probability distribution in agreement-space and try not to observe you.
 
2013-08-26 08:02:35 PM

illannoyin: I don't know why this took so long. It's a perfectly simple equation...

[850x461 from http://www.nothingaboutpotatoes.co.uk/pics/Things088-serious-man-equat ions.jpg image 850x461]


moviesmedia.ign.com
You can't be serious. Man.

/good movie
 
2013-08-26 08:06:31 PM
Heisenberg just sent the cat to Belize.
 
2013-08-26 08:07:33 PM
You're all a bunch of Luddites. Science is just a bunch of ideas and stuff, and computers got better and a scientist was wrong once, so anything is possible.

Go back to your caves.
 
2013-08-26 08:13:35 PM

Quantum Apostrophe: ou're all a bunch of Luddites. Science is just a bunch of ideas and stuff, and computers got better and a scientist was wrong once, so anything is possible.


Please seek help, anti-space-sphere.
 
2013-08-26 08:16:49 PM

Felgraf: lifeboat: But I thought I've also read that an entangled particle can be manipulated -- you can change the spin, for example -- and the other particle will follow suit instantly. Does this not imply FTL communication? Could you not devise an apparatus that communicates intentional changes to a particle's state?

This is the part that's wrong. This *IS* how it works in sci-fi.. but, as it turns out, this isn't how it works out in reality.

This is where a lot of the confusion comes from.


What he said, except even more so. Suppose you create two entangled electrons, and send one to Alice and the other to Bob. Because electrons are quantum particles they always have a spin of exactly plus or minus 1 (for appropriate choice of units). If Alice measures her electron along the up/down axis and gets +1 in the "up" direction she can confidently state that Bob will get "down" (or -1) from the same experiment, because they are entangled. So far so good.

However here's the confusing part where quantum mechanics completely departs from any classical analogy. Alice measuring her electron's spin as up does not cause Bob's electron to have spin down in any classical sense. Bob can still measure the spin of his electron along any axis he chooses. If he happens to choose the same up/down axis -- perhaps by prior arrangement with Alice -- he will certainly get down as his result. But if he chooses some other axis, something totally non-classical will happen. He will measure plus or minus 1 along whatever axis he measures on -- because any measurement of an electron's spin always results in plus or minus one. Alice measures Spin Up, but Bob does not measure Spin Down.

Note that this is entirely different from what would happen if we had two classical objects, say two basketballs spinning in opposite directions. If Bob measures the spin of his basketball on some other axis, he will get a number that is less than 1 (and maybe even 0 if he measures perpendicular to the up/down direction). That's how classically spinning objects behave.

Now what makes this really interesting is that when Alice makes her up/down measurement the result will be completely random; but when Bob makes his off-axis measurement, the result is not completely random. Suppose he measures at 45 degrees off the vertical. Because the electrons were entangled, his result is more likely to point in the direction closer to the down direction ("downish", if you will) than it is to point in the upish direction. He might get either, but he's more likely to get downish -- and QM tells you exactly how much more likely. In the jargon, the results are correlated.

Here comes the really brilliant part: John Stewart Bell realized that the amount of correlation predicted by QM was different from any possible "classical" theory (we can define exactly what we mean by "classical" here, but it's too long for this post). This is called Bell's Theorem or sometimes Bell's Inequalities. And he proposed that this would be an effective test of whether QM was correct: If you ran the experiment many times, the number of times you got downish versus upish would tell you whether QM was correct, or whether (as Einstein and others suspected) there was some deeper, purely classical theory for which QM was an incomplete approximation. Years later, Alain Aspect and his team were able to perform the fiendishly difficult experiments and demonstrated that QM is correct. (Technically speaking, you have to give up either "realism" or "locality", or both).
 
2013-08-26 08:29:34 PM

kahnzo: czetie: Memo to everybody: if your supposed explanation of Schrodinger's thought experiment includes something called a "measurement" (or an "observation"), it's already wrong. And if it includes "wave function collapse", it's doubly wrong.

None of these things has any definition or description in quantum theory, they are just useful approximations for describing what is happening in most practical circumstances. But you can't use them to probe the foundations of QM; that requires you to be precise.

So what's your preference?  Ensemble? Transactional? Many Worlds?  Consistent Histories?
You can't say "You can't do that!" and then lift your skinny fists like tiny antennas to heaven.

The problem doesn't go away because we can do things with more precision.  In fact, violations of Bell's Inequality are quite beautifully astounding, but in no way offer a satisfying resolution to the underlying weirdness.


There's no getting away from the weirdness of QM, regardless of what interpretation you prefer. It just does things that have no classical analogy. If you're looking for a satisfying resolution to the underlying weirdness, well, you will have to get used to disappointment.

Having said that, I think that Many Worlds has the most promise, although it's still incomplete. It doesn't help, though, that most people completely misunderstand what Many Worlds actually says. Sean Carroll explains it far better than I ever could. The neat thing about Many Worlds, properly understood, is that it has the potential to explain both what is happening at a proper fundamental level and why the apparent macro world is so closely approximated by classical physics in which waves have "collapsed". But any interpretation that accords a special place to measurement or observation that is somehow different from "a whole lot of interactions, each of which individually is quantum" is definitely not fundamental (which was precisely Schrodinger's point.)

/In my youth I was partial to de Broglie/Bohm pilot wave theory, and in my heart I still wish it were tenable.
 
2013-08-26 08:31:21 PM

czetie: Felgraf: lifeboat: But I thought I've also read that an entangled particle can be manipulated -- you can change the spin, for example -- and the other particle will follow suit instantly. Does this not imply FTL communication? Could you not devise an apparatus that communicates intentional changes to a particle's state?

This is the part that's wrong. This *IS* how it works in sci-fi.. but, as it turns out, this isn't how it works out in reality.

This is where a lot of the confusion comes from.

What he said, except even more so. Suppose you create two entangled electrons, and send one to Alice and the other to Bob. Because electrons are quantum particles they always have a spin of exactly plus or minus 1 (for appropriate choice of units). If Alice measures her electron along the up/down axis and gets +1 in the "up" direction she can confidently state that Bob will get "down" (or -1) from the same experiment, because they are entangled. So far so good.

However here's the confusing part where quantum mechanics completely departs from any classical analogy. Alice measuring her electron's spin as up does not cause Bob's electron to have spin down in any classical sense. Bob can still measure the spin of his electron along any axis he chooses. If he happens to choose the same up/down axis -- perhaps by prior arrangement with Alice -- he will certainly get down as his result. But if he chooses some other axis, something totally non-classical will happen. He will measure plus or minus 1 along whatever axis he measures on -- because any measurement of an electron's spin always results in plus or minus one. Alice measures Spin Up, but Bob does not measure Spin Down.

Note that this is entirely different from what would happen if we had two classical objects, say two basketballs spinning in opposite directions. If Bob measures the spin of his basketball on some other axis, he will get a number that is less than 1 (and maybe even 0 if he measures perpendicular to the up/dow ...


Aye, the really twisted thing about the experiment (if I recall corectly), is that the only thing it *really* disproved was local hidden variable theory.

Which means, technically, one could still have a 'hidden variable' theory... but it would have to be a *non local* hidden variable, and trying to figure out how that would work makes my head hurt and there is a REASON I am an experimentalist, and not a theorist.
 
2013-08-26 08:36:11 PM

Mad_Radhu: Heisenberg just sent the cat to Belize.


THAT CAT IS FAMILY!
 
2013-08-26 08:42:53 PM

Felgraf: Quantum Apostrophe: ou're all a bunch of Luddites. Science is just a bunch of ideas and stuff, and computers got better and a scientist was wrong once, so anything is possible.

Please seek help, anti-space-sphere.


How dare you? Clearly this story will lead to teleportation, free food and colonizing the universe. Oh, and "anti-space-sphere "? Is your Haloperidol past its best-by date?
 
2013-08-26 08:48:11 PM

Quantum Apostrophe: Felgraf: Quantum Apostrophe: ou're all a bunch of Luddites. Science is just a bunch of ideas and stuff, and computers got better and a scientist was wrong once, so anything is possible.

Please seek help, anti-space-sphere.

How dare you? Clearly this story will lead to teleportation, free food and colonizing the universe. Oh, and "anti-space-sphere "? Is your Haloperidol past its best-by date?


Nah, probably won't lead to that. But it might, since atoms don't age, so immortality.

And by "Anti-space-sphere", I mean... just that. You are like the evil universe version of the Space Sphere from portal 2. You are obsessed with not-going to space. To the point where you rant about it in unrelated threads like this one.
 
2013-08-26 08:54:38 PM

justtray: kahnzo: I'm not sure I agree, completely, as, I think that non-locality IS strange.

I think you mean awesome.

It breaks faster than light travel. Two points in different places can share information simultaneously.


Nope. For reasons too complicated to type out on my phone, it's still impossible to transmit information faster than the speed of light
 
2013-08-26 08:55:11 PM
i35.tinypic.com
 
2013-08-26 08:56:08 PM
i291.photobucket.com

Alright, the cat's alive! Let's go to dinner.....
 
2013-08-26 09:03:16 PM

murray208: kahnzo: I have to say that I like Dr. Hobson's approach.  He attempts to teach quantum physics without paradoxes by suggesting that it's the nature of our assumption of what a particle is that leads to the paradoxes, but if we, instead think of the fields as fundamental and the particles as the fuzzier concept - a localized exchange of information about what's happening in the field - the the paradoxes resolve themselves.

I'm not sure I agree, completely, as, I think that non-locality IS strange.  He may have gotten rid of the paradoxes, but not the oddity.

How is what you described different from the Copenhagen interpretation?


Weird. I've always pictured physicists to be more the pipe smoking type.
 
2013-08-26 09:19:16 PM
I posit there is no cat in the box at all. The cat snuck out when you back was turned.
 
2013-08-26 09:42:11 PM
And we'll describe it in a tiny font, so people will realize just how important and super-serial this discovery is.
 
2013-08-26 10:12:57 PM

born_yesterday: Mad_Radhu: Heisenberg just sent the cat to Belize.

THAT CAT IS FAMILY!


i.qkme.me
 
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