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Improvements in Teleportation
assaultriflesforfree writes "Here's a little update on quantum entanglement and teleportation from The New York Times (free registration, yay): 'Employing a facet of quantum mechanics that Albert Einstein called "spooky action at a distance," scientists have taken particles of light, destroyed them and then resurrected copies more than a mile away.' I am a little skeptical about the Heisenberg Uncertainty Principle statements, though. Is this really a form of Star Trek's Heisenberg Compensator?"
Here's an article from National Geographic that doesn't require registration. Sorry I couldn't find the Google News link for the NYT article.
(from Anonymous Karma Whores R Us)
Light Particles Are Duplicated More Than a Mile Away Along Fiber
By KENNETH CHANG
Employing a facet of quantum mechanics that Albert Einstein called "spooky action at a distance," scientists have taken particles of light, destroyed them and then resurrected copies more than a mile away.
Previous experiments in so-called quantum teleportation moved particles of light about a yard. The findings could aid the sending of unbreakable coded messages, which is limited to a few tens of miles.
The new experiment used longer wavelengths of light than earlier ones, letting the scientists copy the light through standard glass fiber found in fiber optic cables.
"The central issue is to move to telecom fibers and telecom wavelengths and telecom technology," said Dr. Nicolas Gisin, a physics professor at the University of Geneva and the senior author of an article today in the journal Nature. "This then allows us to go the long distance."
The experiments are a primitive realization of the transporter in the "Star Trek" television series that beams people from starship to planet. In coming years, it may be possible to use teleportation to imprint the exact quantum configuration of one atom to another. But teleporting something from the everyday world like a person that contains more than a trillion trillion atoms is highly unlikely, if not impossible.
Even with the light particles, photons, about one in a thousand were received at the other side.
"You're not very sure to arrive," a researcher, Dr. Hugo Zbinden, said about human teleportation.
Still, the experiments show that scientists can overcome a seemingly insurmountable conceptual barrier, the Heisenberg uncertainty principle. The principle states that the location and velocity of a particle cannot both be precisely measured at the same time. That would seem to make it impossible to teleport anything, even single particles, because without knowing their exact specifications they cannot be copied somewhere else.
Devised in 1993 by scientists led by Dr. Charles H. Bennett of the I.B.M. Thomas J. Watson Research Center in Yorktown Heights, N.Y., quantum teleportation produces pairs of "entangled" light particles that can be thought of as a pair of encoding and decoding rings. A message is combined with the encoding light particle. That combination goes to the recipient, who uses the decoding photon to decipher the message. Because no one else has the decoding photon, no one else can decipher the message.
Other encoding techniques using quantum cryptography are simpler, and a more immediate use for teleportation would be as a repeater. Photons almost all peter out after traveling about 50 miles through optical fiber. Teleportation would enable the creation of copies every 50 miles or so, letting the message be sent across an unlimited distance.
teleport your ass over here and get a reg free link
You look in Schrodingers box to check on the cat. Now if you'd entangled the cats. Then let them seperate moving the boxes to hither and yawn, they're still both living and dead. They haven't been made to choose. But once you look in on one of the entangled cats, you can infer the state of the other. So even though it's far away, and doesn't seem like it should have been made to choose, it was.
This is better:
You put two cats in a closed box with a poison cat treat (only 1). Only one of the cats will eat the treat, you don't know which.
Then the cats are seperated into two closed boxes and seperated.
While the boxes are unopened, you don't know the state of either cat.
If you open one box, you then know the state of the other cat.
This is defnitely kind of cool, but I will be a great deal more impressed when it is achieved with an object with appreciable mass.
;-)
A moving photon behaves as though it has mass and momentum. Consider the Compton effect, where a photon striking an electron causes the photon to scatter off the electron like a billiard ball. It's all about quantum theory.
Karma: Excellent (In Soviet Russia, karma pimps YOU)
My point? It is one thing to teleport a photon, which is a massless boson. It is quite another thing to teleport a massive fermion, let alone a collection of them as would be found in any massive object of appreciable size. The physics of teleportation would most likely be very different, since the quantum mechanics and statistics of bosons are quite different from those of fermions. So don't get your hopes up yet regarding teleportation a la Star Trek.
No, this is not a form of Star Trek's Heisenberg Compensator. The whole point of Heisenberg Uncertainty is that it is fundamental and unavoidable. You can get down to that magic h-bar/2pi, but no further. Period.
...
If you could get around that uncertainty issue, it would blow away quantum cryptography entirely; the beauty of it from a security standpoint is that any eavesdropping can be detected, because observing the qubits (in this case, photons with particular spin) necessarily disrupts a certain portion of them.
Yes, this means that a determined eavesdropper could mount an effective DoS by reading all the bits, but with that kind of access, there are easier ways. (Uh, how about cutting the fiber?)
And it's not really teleportation. It's still fundamentally limited to the speed of light. "Teleporting" anything more complicated than a hydrogen atom is going to be insane due to (here it comes again) Heisenberg Uncertainty - you have to extract its state, but you can't do that to within that certain magic tolerance
Ok, before everyone freaks, Quantum Teleportation isn't what most think it is. I've had a class and attended a few lectures by renowned Gilles Brassard from the University of Montreal, one of the founder of the field and especially quantum encryption, along with Charles H. Bennet from IBM and many others.
t at ion/
u an tumintro/brassard/2/
First, "teleportation" only teleports "DATA", quantum information, like the spin of an electron. You won't see any beam me up scotty, despite how much people wants to and how wrong reporters are in artciles =)
Second, here's a VERY brief info page on Quantum Teleportation on IBM's page:
http://www.research.ibm.com/quantuminfo/telepor
For more in depth info, try to find articles in magazines and books, especially one written by Charles H. Bennet and/or Gilles Brassard.
One lecture by Brassard can be found online here, there's even a PDF:
http://www.msri.org/publications/ln/msri/2002/q
They will explain this much better than my understanding will do. It's MUCH funnier and interesting when Brassard presents it, and it's MUCH harder to understand too. The few pictures and bits at the begining of the lecture are what Quantum Teleportation is NOT. Even renowned scientific publication are fooled by bad journalism, and even IBM went over it's head with this, it's kinda funny =)
Anyway, "Beam me up Scotty" will never result from Quantum Teleportation, so don't hold your breath =) The article briefly states this tho, but only seems to gloss over it and even says "maybe", which is completely wrong.
Also, Brassard stated MANY times that is does not violate ANYTHING, and especially not Heisenberg uncertainty principle. The original DATA must be destroy, then it is "rebuilt" on the other side, and because of a property of EPR, "entanglement", you never mesure the quantum information completely, thus not violating Heisenberg uncertainty principle.
One last note, the following bit on the article is probably the most simplistic non-explanation of what is Quantum Teleportation:
"A message is combined with the encoding light particle. That combination goes to the recipient, who uses the decoding photon to decipher the message. Because no one else has the decoding photon, no one else can decipher the message."
Not quite. That's more like a 'hidden variable' version of Quantum Mechanics. The box that the poison treat is in is a hidden variable because it has a definite value (albeit unknown to you). The standard interpretation of Quantum Mechanics is that there are no hidden variables. So the poison treat would have to be simultaneously 'in both' and 'not in both' boxes until you observe one of the cats.
The original Schroedinger's Cat thought experiment used a truly quantum-mechanical device to determine whether the cat should live or die. I don't think you can remove that quantum element and still have a valid analogy. The point (or one of them) of the thought experiment is that the cat 'magnifies' the quantum effect.
This isn't a transporter story, this is a story about secure communications.
If you can transmit messages with entangled photons over an optical network, you can prevent anyone from "tapping" the line and observing your communication without you knowing. If someone fucks with one of the entangled photons, the other party will know.
It shouldn't be. Light does have momentum (part of the idea behind solar sails). However, light does not have mass (but you might be able to argue that since it has momentum it behaves like it has mass, whatever that means). Most people think that this cannot be since p=m*v and if it has no m, it can't have any p. Well, relativity shows that E=p*c for light so if the light has energy, it can have momentum. In this way, momentum is more of a fundamental quantity than mass or velocity and cannot, in general, be separated into a product of the two.
That's not true in the quantum world. In the quantum world the jelly beans don't know which color they are, in fact they are BOTH colors. It's not until they are actually exaimned that they decide which color they are and retoractivly enact that policy. This is the idea behind quantum encryption. The act of reading the key changes it, therefor if anyone taps into the signal, and reads it, both parties (sender and reciever) know that the line has been comprimised. If your still confused I would recommend a book on quantum computing. Most will give a HUGH description on this, more then I care to give here. The man thing to remember is that the Jelly Beans are qubits....not jelly beans. Therefore your assumptions about jelly beans don't hold true.
Light has momentum: true.
Light doesn't have mass: false.
Light has mass because light has energy. Mass and energy are the same quantity expressed in different units. The conversion factor from mass to energy is c-squared.
What light doesn't have is rest mass.
Paul
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