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.

Comments

Re:I Think this article might be a bit misleading.

[Anonymous Coward]

There's no need to be a nerd about it. Some people mistakenly think this news is about fast internet speeds.
some people see "teleported their information" and skim the rest of the article.

Re:Quantum Entaglement is not strange at all

[wonkey_monkey]

Not really, but if you want a completely descriptive analogy for quantum entanglement... well, there isn't one.

Alice and Bob have two different ways of measuring particles, and each way can give two different results. They might do a "brightness" measurement (analogy) which returns either black or white. Or they might do a "colour" measurement, which returns either red or blue.

The trick is that, although you might think the results are predetermind, and therefore fixed, they're not. If Alice does a brightness measurement and Bob does a colour measurement, there is now no way for Alice to get a colour measurement that will definitely match Bob's. The information is gone. It might match by chance, but it equally might not.

So Alice and Bob measure at random - sometimes brightness, sometimes colour. Later they compare notes on which tests they made on which photons (they can do this in public), and discard any results where they didn't use the same test. The remaining results are what they use to make up their key - a 0 for black-or-red, a 1 for white-or-blue.

If they do a test encrypt, and find that it doesn't work, that indicates someone else was intercepting their photons and screwing up the entanglement (because that person would have no way of knowing whether to test for brightness or colour).

At least, that's my understanding. I could be wrong, and probably am.