Quantum teleportation over 143 kilometres using active feed-forward

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11472.html

by antimora • 14 years ago

61 64 14 years ago

I confess I haven't read the entire article, but from the abstract I was wondering, why 143 kilometers (they answer this: distance to satellites), and why those two islands (except to maybe show off that they were teleporting in the lap of luxury)? I'm guessing it's because there is no physical link between the two, so it will reduce skeptics' abilities to say "this is a hoax, there is a cable connecting the two stations."

ricardobeat• 14 years ago

But quantum teleporting does require a link between the two points. From the Wikipedia article:

    The prerequisites for quantum teleportation are a qubit
    that is to be teleported, a conventional communication
    channel capable of transmitting two classical bits (...)

There is no teleporting in the classical meaning of the word, just communication between two locations to make a remote qubit match the (unknown) state of the local one. That state is 'teleported'.

javert9• 14 years ago

There is no teleporting in the classical meaning of the word

So isn't it dishonest to call it teleportation? Even if all the scientists working in this area are calling it that?

moondowner• 14 years ago

Beam me up, Scotty! (I couldn't resist...)

jstalin• 14 years ago

Could someone translate the abstract into English?

antimora• 14 years ago

Here is another article that tries putting in English.

http://www.zmescience.com/science/physics/physicists-quantum...

dandrews• 14 years ago

Careful with this article. They get it wrong, suggesting the possibility of "instantaneous internet connections". No FTL information transfer allowed, kids.

alecco2• 14 years ago

The author fails to understand the basics of Quantum Teleportation. Think of it this way: Alice has 2 boxes with the same unknown bit, and sends one of those boxes to Bob. When Alice opens her box she can see the value and Bob can see it too. Something like that.

Very good for cryptography (think untamperable shared secret keys) and for some cases of parallel computing.

Superluminal (FTL) communication would break Special Theory of Relativity. If anybody achieves that it would be an instant Nobel and front page on every newspaper on the planet. Even a mistake like the FTL neutrinos fiasco earlier this year.

Tech journalists tend to skim the abstracts and hype it to sell more clicks/ads.

newhouseb3• 14 years ago

Is it incorrect to say that, with quantum teleportation - while faster than light travel of _matter_ is impossible, faster than light travel of _information_ is possible provided that you have previously shipped the endpoints of the link?

alecco2• 14 years ago

http://en.wikipedia.org/wiki/Quantum_teleportation

First paragraph.

newhouseb3• 14 years ago

Thanks, the key sentence here is

> However, it does not _immediately_ transmit classical information.

As I understand it, once you distribute an EPR pair, you can transmit one qubit of quantum information which thereby destroys the pair. Provided you can encode your classical information into quantum information, the amortized rate of classical information communication cannot be faster than light because you need to first distribute the EPR pairs (which you cannot do at FTL), but the _instantaneous_ rate of classical information communication could be faster than light.

The biggest assumption here is that you can encode/decode classical information to/from quantum information at a rate (if at all) faster than it would take for matter to travel over the potentially infinite distance between the EPR pair. Some googling reveals that this is possible via means such as time-bin encoding. (Edit: time-bin is only for photons, which I don't know if you can entangle, but it still appears that you might be able to encode classical information in electron spin)

What am I missing?

Edit - alecco's other answer in this thread make it much more clear what is going on. Thanks again.

Saavedro3• 14 years ago

Yes. It is incorrect to say that.

The term "Quantum teleportation" just refers from moving quantum information from one place to another, which happens to be kind of hard. In fact, in order to do it we "piggyback" on classical information, so it is by definition subject to all the same limitations of classical information transfer.

smosher4• 14 years ago

There's no such thing as F-T-L travel of anything. It's okay though, the quantum information is not traveling.

walrus• 14 years ago

Some previous discussion: https://news.ycombinator.com/item?id=4485347

elorant• 14 years ago

I find it extremely intriguing that although we do not fully understand the fundamentals of the quantum world we are able to exploit it.

jvdh• 14 years ago

The full article is also available on Arxiv.org: http://arxiv.org/pdf/1205.3909v1.pdf

kalmsy• 14 years ago

"... whose location is unknown ..."

Wait. Is this the dawn of truly anonymous communication, with no means of tracing the origin or target by wiretap?

Quantum teleportation over 143 kilometres using active feed-forward

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