Exploring Quantum Entanglement: Teleportation & Beyond

[iRaid]

Can anyone explain to me how quantum teleportation can be achieved through quantum entanglement? I read a few days ago that scientists finally "teleported" light and I read up on it and it said something about quantum entanglement. A quick wiki search brings up something I really don't understand, so a simpler, yet in depth answer would be very appreciated. Btw, this just really seems impossible to destroy something in one place and make it reappear in another..

Article: http://www.postchronicle.com/news/original/article_212360585.shtml
Wiki: http://en.wikipedia.org/wiki/Quantum_entanglement

Thank you.

 

[Kainen007]

I think it may help you to think of the objects not being destroyed but taken apart and you should get a idea of how its done from that.

 

[Kainen007]

Just for the record its not really Telepotation its more like Traveling hitching a lift if you like.

 

[rodneyjnorris]

Einstein called this: Spooky action at a distance. basically, first it is easier to think of the concept with physical objects but realize that mostly we are talking about energy states. (information). I just had this discussion with my 13 yr old son so I will be basic. 1. We do not know why nor how it works, just that it does and how to manipulate it so as that it is observable. 2. think of it like two cards each with a blue side and a red side. If we entangle the two cards then they are opposite each other in other words one card would be face up blue and the other face up red. Once the two are entangled it appears to be irrelevant where or how far apart the two are, if you change the state of one (from blue side up to be red side up), then other changes instantaneously to the opposite, from red side up to blue side up). How the two "know" the other has changed is not known but suffice it to have been proven that the other card will "flip" to the other side. Now, we can't entangle cards, only Very Very small particles but to illustrate what happens logically, and really it is an energy state, high or low. But... This is eternally useful for long distance communication. Computers or anything digital for that matter, describe everything using only two states, on/off, 1 or 0. entangle thousands of "pairs" and keep the first half of each pair here on Earth and send the second half on a star-ship to another galaxy and monitor each "half pair" and voila instant communication since if you change the state of the parts hear on Earth the states change on the star-ship instantaneously providing real time communication. Teleportation, really we are talking about information and reconstructing a copy using the information. We can entangle two particles and manipulate them and observe them but we do not know how the other half "knows" to change states if we change the state of the other. "Changing" the state is done simply by observing one half of the pair. The other state is then known. Hope this helps to get the general idea

 

[ZapperZ]

Wow!

I seriously didn't want to stick my nose into this one, but holy cow! After seeing the responses, I think I have to say something before this goes off the deep end, until others such ad Dr. Chinese can come in and provide a more detailed explanation.

Can anyone explain to me how quantum teleportation can be achieved through quantum entanglement? I read a few days ago that scientists finally "teleported" light and I read up on it and it said something about quantum entanglement. A quick wiki search brings up something I really don't understand, so a simpler, yet in depth answer would be very appreciated. Btw, this just really seems impossible to destroy something in one place and make it reappear in another..

Article: http://www.postchronicle.com/news/original/article_212360585.shtml
Wiki: http://en.wikipedia.org/wiki/Quantum_entanglement

Thank you.

I will start with something very simple that we already know from classical physics that does not cause any mystery. It should provide you with a naive picture of quantum entanglement.

Say you have an object, and it isn't spinning. So its initial angular momentum is zero, and that is known. Say at some point, it explodes into two objects, A and B, and both of them move in opposite directions to each other. At some distance away, a person decides to measure Object A to see if it has acquired an angular momentum of some kind. As soon as he knows the angular momentum of A, he IMMEDIATELY knows the angular momentum of B, because of conservation of angular momentum.

So far so good, and there's nothing weird or strange about this one.

So how is this different in QM? In QM, what makes this "strange" is a concept that is inherently built-in - superposition. It says that before a measurement is made, a quantum system can be in a simultaneous state of all the possible outcome. This is important, because this is well-established as one of the principles in QM.

So if we go back to our original example, for a QM system, when the original object splinters into two quantum particles, each of the particle, depending on the system, can be in a superposition of states. For an electron, it may be in a +/- 1/2 spin state, for example. So both A and B are in a superposition of states as they shoot off in opposite direction, their spin states consisting of both outcomes, and not determined, before a measurement is made.

But when a measurement is made on A, and we now have caused A to be in a particular state, somehow B "knows" what was measured and it assumes the appropriate state so that both the measurements of A and B preserve the conservation laws of the original particle. This is what makes it "weird" and what makes it different than the classical situation.

This is one example where one cannot learn physics in bits and pieces. One cannot understand quantum entanglement without an understanding of quantum superposition. And one cannot understand quantum superposition without understanding quantum operators (First Quantization), etc.. etc. They are all related. And of course, one won't know that this is "weird" without understanding classical mechanics first.

Zz.

 

[zonde]

Can anyone explain to me how quantum teleportation can be achieved through quantum entanglement? I read a few days ago that scientists finally "teleported" light and I read up on it and it said something about quantum entanglement. A quick wiki search brings up something I really don't understand, so a simpler, yet in depth answer would be very appreciated. Btw, this just really seems impossible to destroy something in one place and make it reappear in another..

Article: http://www.postchronicle.com/news/original/article_212360585.shtml

This article is crap. So it would be very bad idea to take it as a starting point for learning anything.

Original article:
http://www.sciencemag.org/content/332/6027/330.abstract?sid=8a1bdc75-1144-4852-a1ba-ff19a3ddc491"
This too sounds "interesting". The only thing you can "teleport" in QM is quantum state. Not wave packets, not light and definitely not bits of light as that article of yours is claiming.

 

[JesseM]

Original article:
http://www.sciencemag.org/content/332/6027/330.abstract?sid=8a1bdc75-1144-4852-a1ba-ff19a3ddc491"
This too sounds "interesting". The only thing you can "teleport" in QM is quantum state. Not wave packets, not light and definitely not bits of light as that article of yours is claiming.

In the standard version of QM (as opposed to some alternatives like Bohmian mechanics) there's no meaningful difference between teleporting the full quantum state of a system and teleporting the system itself, to differentiate them would in effect be to endorse some kind of hidden variables theory where particles have distinct "identities" even though this can't be determined by any possible measurement, see my comments in [post=3162115]this post[/post] along with the subsequent discussion with ZapperZ.