I know, I know. But is it my fault I'm intelligent and handsome?

It's a curse, really (obviously you'll have to take my word for it).


wanna cyber?

Ok physics weenies, here's a challenge for you. Explain quantum teleportation to me.

As I understand it, you can transfer a quantum state to pretty much anywhere instantaneously. However, this doesn't involve the transfer of matter, energy or information beyond that quantum state.

I guess what I'm really asking is: is there a possibility of this being used for practical purposes, for instance if they ever build a properly functioning quantum computer will they be able to use it to send information instantaneously?

I'm not a physicist, so I can't really explain the math to you, but quantum teleportation does not allow transfer of information at superluminal speeds.

But don't take my word for it: http://en.wikipedia.org/wiki/Quantum_teleportation

It is my understanding that if you analyze the math, superluminal communication will require one to violate either general relativity, or causality.

Relativity is pretty solid, but few people want to admit causality can be violated because that pretty well invalidates the whole of human logic. However, I've read thought experiments by people much more informed than myself that show that while the standard model holds, causality is not as iron clad as we'd like to think.

Personally, I do believe that quantum computation will be a reality within this century, and I also believe that superluminal communication and flight, and therefore time travel are also quite possible. Consider, it wasn't that long ago that Lord Kelvin declared heavier than air flight a physical impossibility.

wanna cyber?

I normally don't like scientists, but you're okay.

Ok physics weenies, here's a challenge for you. Explain quantum teleportation to me.

As I understand it, you can transfer a quantum state to pretty much anywhere instantaneously. However, this doesn't involve the transfer of matter, energy or information beyond that quantum state.

I guess what I'm really asking is: is there a possibility of this being used for practical purposes, for instance if they ever build a properly functioning quantum computer will they be able to use it to send information instantaneously?

It's late, but here's the jist of it:

As an example, let's say two particles are entangled so that when one is spin up, the other is spin down. You have no way of knowing which one is which until you observe one. And the particles are like 70 billion miles away.

You check the particle at your end. Spin up. The other one must be spin down, then. You know this, but your friend at the other end of the galaxy has no clue and you have no way of telling him.

So it's not really teleportation.

It is my understanding that if you analyze the math, superluminal communication will require one to violate either general relativity, or causality.

Relativity is pretty solid, but few people want to admit causality can be violated because that pretty well invalidates the whole of human logic. However, I've read thought experiments by people much more informed than myself that show that while the standard model holds, causality is not as iron clad as we'd like to think.


If you believe Einstein's general and special relativity, then causality cannot be violated.

The question becomes... was Einstein wrong? (http://www.einsteinwrong.com/)

It's late, but here's the jist of it:

As an example, let's say two particles are entangled so that when one is spin up, the other is spin down. You have no way of knowing which one is which until you observe one. And the particles are like 70 billion miles away.

You check the particle at your end. Spin up. The other one must be spin down, then. You know this, but your friend at the other end of the galaxy has no clue and you have no way of telling him.

So it's not really teleportation.

Thanks. That's a really good, concise explanation.

You don't really do physics at all do you?

bornsceptic: Quantum teleportation will become useful when we learn how to affect the spin on our end, thus being able to send messages a la morse code with entangled particles. Let's look at this example:

I want to send a short message in morse code to someone 70 billion miles away. They have a machine which pulses an entangled particle to test it's spin every 1/4 second. On my end, I can affect the spin with my machine every 1/4 second if needs be. We agree that a reading of "up" on their side is 0 or null, "down" is 1 or a signal. We also agree that a signal of shorter than 3/4 second is a dot, longer than 1 seconds a dash, just so that our machines can be out of phase on readings, but still get accurate measures due to the buffer on reading. I will pulse every dot for 3/4 seconds exactly, and every dash for 1 1/4 seconds exactly, so that any loss of signal will still put the signal term into constraints readable by the code (since an every 1/4 second reading can only error on a term of less than 1/4 second).

I pulse my particle for 3/4 seconds, then rest it for a half second, then pulse it 3/4 more, then rest 1/2, then pulse 3/4 more. Morse code reads this as an "S". I have just sent information 70 billion miles in the span of 3 1/2 seconds.

Problems: Measuring a quantum state perturbs the state and makes it unstable. Hence, one-time usage. Likewise, it also (theoretically, or so I've read) destroys the quantum pairing to meddle with it in such a manner. There are a vast array of other issues. The wiki page explains most of them.

What we should really be looking at is Casimir Effect.

"Exotic matter with negative energy density is required to stabilize a wormhole.[6] Morris, Thorne and Yurtsever[7] pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time, and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel." (Taken from the wiki site on Casimir Effect.)

Then again, almost all forms of "teleportation", wormhole manipulation, or superluminal speed travel/information involve Planck energies which are unattainable to us. So, it's all pretty moot from a standpoint of Physically, but pretty fun to think about theoretically.

Thanks. That's a really good, concise explanation.

You don't really do physics at all do you?

It was fucking late, and now it's fucking early. Shut up.

Please... ?

bornsceptic: Quantum teleportation will become useful when we learn how to affect the spin on our end, thus being able to send messages a la morse code with entangled particles. Let's look at this example:

I want to send a short message in morse code to someone 70 billion miles away. They have a machine which pulses an entangled particle to test it's spin every 1/4 second. On my end, I can affect the spin with my machine every 1/4 second if needs be. We agree that a reading of "up" on their side is 0 or null, "down" is 1 or a signal. We also agree that a signal of shorter than 3/4 second is a dot, longer than 1 seconds a dash, just so that our machines can be out of phase on readings, but still get accurate measures due to the buffer on reading. I will pulse every dot for 3/4 seconds exactly, and every dash for 1 1/4 seconds exactly, so that any loss of signal will still put the signal term into constraints readable by the code (since an every 1/4 second reading can only error on a term of less than 1/4 second).

I pulse my particle for 3/4 seconds, then rest it for a half second, then pulse it 3/4 more, then rest 1/2, then pulse 3/4 more. Morse code reads this as an "S". I have just sent information 70 billion miles in the span of 3 1/2 seconds.

The fault in this idea is thinking that you affecting your particle will somehow affect their particle.

Entanglement is a state where you can't represent an n-particle wavefunction by breaking it down into products of their individual wave-functions.

Yeah, necroth's morse code idea was kind of what I thought in terms of information transfer but obviously there are theoretical problems as well as practical.

Poops: Thanks for setting that straight, as the descriptions that Kaku gives for quantum teleportation always seemed like my example. I knew that entanglement was extremely volatile and easily destabilized, and there's alot of information on the various paradoxical reasons we shouldn't be able to accomplish it.

Thread-necroed to add

http://www.process.org/discept/2008/02/25/expulsion/

Read this earlier in the week:
http://www.sciencemag.org/cgi/content/full/319/5866/1034

Kind of sad, actually.

Read this earlier in the week:
http://www.sciencemag.org/cgi/content/full/319/5866/1034

Kind of sad, actually.

Good for you. I don't have a subscription, so I can't read it.

Oh. It was one of their news items so I figured it would be freely available.

I suppose you could copy and paste, or is reposting of copyrighted works verboten around here?