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Quantum Teleportation Achieved Over 7km of Cable (sciencealert.com)
An anonymous reader quotes a report from ScienceAlert: Quantum teleportation just moved out of the lab and into the real world, with two independent teams of scientists successfully sending quantum information across several kilometers of optical fiber networks in Calgary, Canada, and Hefei, China. Quantum teleportation relies on a strange phenomenon called quantum entanglement. Basically, quantum entanglement means that two particles are inextricably linked, so that measuring the state of one immediately affects the state of the other, no matter how far apart the two are -- which led Einstein to call entanglement "spooky action at a distance." In the latest experiments, both published in Nature Photonics (here and here), the teams had slightly different set-ups and results. But what they both had in common is the fact that they teleported their information across existing optical fiber networks -- which is important if we ever want to build useable quantum communication systems. To understand the experiments, Anil Ananthaswamy over at New Scientist nicely breaks it down like this: picture three people involved -- Alice, Bob, and Charlie. Alice and Bob want to share cryptographic keys, and to do that, they need Charlie's help. Alice sends a particle to Charlie, while Bob entangles two particles and sends just one of them to Charlie. Charlie then measures the two particles he's received from each of them, so that they can no longer be differentiated -- and that results in the quantum state of Alice's particle being transferred to Bob's entangled particle. So basically, the quantum state of Alice's particle eventually ends up in Bob's particle, via a way station in the form of Charlie. The Canadian experiment followed this same process, and was able to send quantum information over 6.2 km of Calgary's fiber optic network that's not regularly in use.
Someone explained this news to me recently, they said the scientists didn't send ~information~ over quantum entanglement, they sent the data across normal networking means and sent and a key to unlock the data via quantum entanglement. The method used has deep implications for security and encryption methods, but not faster than light data transfer. Just wanted to clear that up.
No. This article clearly means we'll be transporting ourselves to Mars before the week is out.
Exactly. We just need to make sure no flies get into the pods before the doors shut.
Given that none of the articles, as far as I saw, said anything about faster than light communication, and one explicitly disavowed the concept, I think you're projecting your own mistaken conceptions here.
And your friend is correct - quantum teleportation has nothing to do with faster than light communication, as you can neither determine to what form the waveform has collapsed, nor whether one side has already collapsed it. It's effectively** equivalent to having two identical letters containing a random message sealed in an envelope, taking them to different locations, and opening them at the same time. Both sides will get the same random message at the same time, but it provides no means for conveying information faster than light. It is however useful for keysharing.
** In the real world, what is written inside the "envelopes" isn't determined until it's actually observed. But it works out to the same net effect.
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Umm, this is Slashdot!
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There's no need to be a nerd about it.
It's effectively** equivalent to having two identical letters containing a random message
No. you're describing entanglement.
Teleportation is subtly different.
Teleportation consists of transferring the quantum state of one particle to another particle via the use of entangled particles (and a classical channel)
The beauty of this is that the entangled state can be set up in advance. You then give me a particle that you might or might not know something about its quantum state (but importantly, I do not know what you know about it so cannot measure that quantum state in advance). I can transfer the state of that particle to another particle that Bob has via some entangled particles we exchanged earlier *plus* some standard classical information that goes over classical channels (it's this classical information that limits the teleportation to the speed of light)
The particle that Bob ends up with is in an identical state the the one you gave me (and which I still have).
N.B. This is quantum teleportation, not quantum cloning which is not possible. The act of getting the quantum state to Bob affects my particle in a way that means I cannot also extract any information from it about the original state of your particle.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.