Quantum Superposition

[Greni]

Dear me what a lovely thread. I was worried I'd see a bunch of illiterates bashing on about the end of the world or something. Escapist community you do surprise sometimes in a good way.

Anyway, just dropped in here to add a little vid:


The relevant part begins at 35:00 and onwards basically. But if you have an hour to spend you would be far better of just watching the whole thing. The lecture is in front of a whole bunch of non-geeks so don't be scared.

It also features Simon Pegg and theoretical physicist Jim Al-Khalili making waves with a jump rope, Jonathan Ross solving math problems and James May lighting his hand on fire with flammable foam.

 

[manaman]

Watch this, it should either help clear things up or make you more confused. Either way it's educational.
http://www.youtube.com/watch?v=DfPeprQ7oGc
Granted, it's not actually about schroedinger's cat but the double slit experiment that gave rise to the observation.

You should really watch the rest of that video sometime. You might not want to use those scenes anymore. The rest of the video is about how the mind controls reality and we all just need to wake up to that fact, and uses "quantum" mumbo jumbo (and a few real concepts, but warps the meanings) to justify that stance.

 

[Pseudoboss]

http://www.youtube.com/watch?v=uWMTOrux0LM
According to this video, Schrodinger's cat is horribly misrepresented in popular culture, because Schrodinger wasn't saying that the cat is both alive and dead, but that there is a pretty big discrepancy on how things act on the Newtonian scale and the quantum scale. Because, the idea of the cat being both alive and dead doesn't make any sense. Where the idea of a particle being in two states at the same time makes perfect sense.

Hopefully this is true, and not a load of crap. I think it makes more sense this way, and I think that it's perfectly possible for the idea of Schrodinger's cat to have been mixed up so horribly that it's saying practically the exact opposite of the idea it was intended to convey. And I can point out a lot of things that have been similarly misrepresented, but that's not for this thread.

 

[Rabid Toilet]

So it seems like superposition doesn't work at the macro scale (by macro I'm going to assume anything bigger than an atom), but Schrodingers' Cat is meant to illustrate how superposition works at the subatomic scale. My main point of contention was that at the macro scale it doesn't seem like there's an "event", like the presence of an observer, that causes the wave function to collapse - in the alive or dead sense of this example, the cat is either alive or dead, it's never "potentially both".

But when it comes to an electron, I instinctively want to believe the same rules of matter apply, but apparently they don't. Superposition is what allows for things like quantum tunnelling and entanglement right? Those are obviously things that wouldn't work under a Newtonian model, but have been observed at the subatomic level.

You're right that superposition doesn't work on a macro scale. It only applies to subatomic particles like electrons.

And no, subatomic particles do not work with a Newtonian model, unless you're looking at them. You're right to want to apply the rules of matter to them, since they're really just tiny balls of matter, but it turns out they work nothing like that. It's really complicated and makes no sense, but that's what we've observed to be happening.

 

[Kordie]

Watch this, it should either help clear things up or make you more confused. Either way it's educational.
http://www.youtube.com/watch?v=DfPeprQ7oGc
Granted, it's not actually about schroedinger's cat but the double slit experiment that gave rise to the observation.

You should really watch the rest of that video sometime. You might not want to use those scenes anymore. The rest of the video is about how the mind controls reality and we all just need to wake up to that fact, and uses "quantum" mumbo jumbo (and a few real concepts, but warps the meanings) to justify that stance.

That's a perfect reason to watch only the clip attached. It shows the double slit experiment and how a particle collapses from superposition to a single state. That there is the basis of schroedingers cat.

http://www.youtube.com/watch?v=uWMTOrux0LM
According to this video, Schrodinger's cat is horribly misrepresented in popular culture, because Schrodinger wasn't saying that the cat is both alive and dead, but that there is a pretty big discrepancy on how things act on the Newtonian scale and the quantum scale. Because, the idea of the cat being both alive and dead doesn't make any sense. Where the idea of a particle being in two states at the same time makes perfect sense.

Hopefully this is true, and not a load of crap. I think it makes more sense this way, and I think that it's perfectly possible for the idea of Schrodinger's cat to have been mixed up so horribly that it's saying practically the exact opposite of the idea it was intended to convey. And I can point out a lot of things that have been similarly misrepresented, but that's not for this thread.

You aren't wrong. It is so mis used that cracked even made an article covering it. http://www.cracked.com/article_19419_6-parodies-that-succeeded-because-nobody-got-joke.html It's number 5.

 

[Rabid Toilet]

Watch this, it should either help clear things up or make you more confused. Either way it's educational.
http://www.youtube.com/watch?v=DfPeprQ7oGc
Granted, it's not actually about schroedinger's cat but the double slit experiment that gave rise to the observation.

You should really watch the rest of that video sometime. You might not want to use those scenes anymore. The rest of the video is about how the mind controls reality and we all just need to wake up to that fact, and uses "quantum" mumbo jumbo (and a few real concepts, but warps the meanings) to justify that stance.

While the movie itself is a load of crap, I believe the experiment they show is pretty legitimate. They just misrepresent the results as "the universe thinking" and stuff like that.

 

[Luca72]

Watch this, it should either help clear things up or make you more confused. Either way it's educational.
http://www.youtube.com/watch?v=DfPeprQ7oGc
Granted, it's not actually about schroedinger's cat but the double slit experiment that gave rise to the observation.

You should really watch the rest of that video sometime. You might not want to use those scenes anymore. The rest of the video is about how the mind controls reality and we all just need to wake up to that fact, and uses "quantum" mumbo jumbo (and a few real concepts, but warps the meanings) to justify that stance.

While the movie itself is a load of crap, I believe the experiment they show is pretty legitimate. They just misrepresent the results as "the universe thinking" and stuff like that.

Haha, you beat me to it. The double slit experiment is interesting and has fascinating ramifications, but I find myself recoiling and hissing uncontrollably whenever I see anything related to that movie. What I'm trying to do with quantum mechanics is understand what has been rigorously studied, and it bugs me when people take those conclusions and just run with them and act like it's "science".

On that note, I know there's validity to the act of observation changing the results of the experiment. But isn't this due to the apparatus being used to detect the movement of the particle?

Also, thanks everyone for clearing up the origin of Schrodingers Cat to me. I tended to skip past the "intent" of the thought experiment and look at the details, and kept coming away with the nagging thought in my head that "this is such bullshit". Reading about the Copenhagen interpretation and the problems with it has cleared a lot up for me.

 

[Chromatic Aberration]

And there I thought that I had to explain that stuff all by myself - but it seems everything that I would have mentioned has already been said. Good.

Still, I'll reiterate: Schrödinger's Cat is a paradox to show the problems when trying to use the mathematical framework in QM on macroscopic scales. Thing is, there still is no completely satisfying answer as to how the macroscopic world emerges from the quantum formalism. Best bet currently seems to be decoherence i.e. information about the state of a particle leaks into the environment through interactions effectively constraining the possible states the particle can be in (like the cat would just be alive or dead and not some crazy zombie (i.e. no superposition state)). Effectively macroscopic determinism (cat is either alive or dead) is in this picture pretty much an emergent property.

Thing is, and that is what I think is something important to keep in mind is that it is very dangerous to try and desperately fit mathematical objects to the reality as we know it i.e. trying to find a representation for some mathematical theory which incidentally perfectly describes what we see. This is predominantly the case in QM where it's objects routinely defy our perception of reality.
As such, one should always take claims about the nature of reality with a grain of salt.