Scientists Report Finding Reliable Way to Teleport Data | Hacker News Reader

Scientists Report Finding Reliable Way to Teleport Data

nytimes.com

52 pointsSnarfDragon21 comments

Mods should switch to the NYT headline ("Scientists Report Finding Reliable Way to Teleport Data"), which is appropriate. The current HN headline ("New Research in Faster-than-light Communication") is out to lunch.

Entanglement is not FTL communication.

Edit (having now skimmed the paper from Spittie http://arxiv.org/abs/1404.4369): Quantum teleportation isn't FTL communication either.

It doesn't even teleport the data. It merely shares the same state—you can't move information through this shared state.

Notice the headline doesn't say teleport information, but instead says teleport data - which is accurate. I agree, the Title on HN is a degraded version of the NYT version.

What is data without semantics? A RNG?

Yes. Done.

Is it an allowed solution to have instantaneous information transfer between distantly separated points if there was a slower-than-light bulk transfer phase beforehand? This is the idea of physically carrying a supply of entangled photons to Alpha Centauri, which might take a hundred years, then enjoying your Netflix streaming in real time until they're all used up.

No. No cheating; quantum mechanics can still be a local theory, for some interpretations (most notably MWI), which forbids such an action.

Any solution that allows for FTL transfer of information violates causality, at least according to relativity. If you can transmit information over entangled photons instantaneously, you can use the time dilation effects of relativity to send information back in time to yourself.

But transferring instantaneously is theoretically possible through this method, correct?

So am I right in interpreting that if we can transfer particles instantaneously, that information time travel must necessarily follow?

If we can transfer information FTL, (backwards) time travel necessarily follows.

See Kip Thorne's time machine schematics (mentioned e.g. here: http://www.andersoninstitute.com/wormholes.html). The only problem is that you need a wormhole to build it.

No, not as far as we know. The no-communication theorem states that you cannot communicate information between observers via entanglement, at least assuming the laws of quantum mechanics hold.

It's too bad that the remarks are focused on the FTL fallacy of Quantum Teleportation instead of the innovation claimed: being able to reliably do QT is a big improvement over the current methods.. If memory serves, I read articles where they said that in their experiments, the QT was successful 20% of the time, obviously this depends on the experience's setup, but 100%? That's a first, AFAIK.

Title of this post does not seem correct. Is this really FTL or is there an at-light-speed signal that must also occur to convey the entangled state?

I'm not certain, but the abstract says We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins. So I think there's a classical setup phase, then the information transfer is instantaneous.

This seems to be the full paper, if anyone can understand it: http://arxiv.org/abs/1404.4369

(If there is a way to make me feel stupid fast is to read those papers).

EDIT: After reading the article, the novelty there is that they entangled particles separated by 3 meters. They didn't achieve any unusaly long entanglement time. That won't (or, at least, it's not trivial how it would) lead to better quantum computers, but could lead to qbit transmission and cloud quantum computers, as the authors say.

The original: From the abstract, they found a way to "freeze" entangled qbits, so that you can transport them, and read later.

For the confusion here, just remember that you can not transmit information by reading quantum entangled pairs. You can use them to make a quantum cryptography key exchange, that's still as subject to man in the middle attacks as symetric crypto, and you can use them for error correction in quantum computers (for what this one may be HUGE).

The title, along with the rest of the article, seems to obscure an important point. Although the entangled particles appear to communicate with each other FTL, the observers can't communicate any information with each other this way. There are still lots of applications of this to quantum computing, but there wouldn't be any way to build an ansible with this.

Question: Is an ansible absolutely impossible for any current theorized method in physics?

I ask in light of current research on FTL travel with alcubierre drives.

The prohibition of faster than light travel (or communication) in GR only applies locally. That is to say, it really should be phrased as "two observers can not have a relative speed faster than c at the same point."

If you're not talking about the same point of space, the space between the observers could be expanding and the rate of this expansion can legitimately be faster than c without violating the relativity principle.

The trick to creating genuine FTL travel or communication is to somehow multiple paths between the same points in spacetime -- i.e. a wormhole. If the new path is shorter than the other, then information can travel along it at a speed less than c, but still take less time than light going the long way.

Quantum entanglement whole different game. Once a measurement has been made, the entanglement is broken and the components are left in a particular state. But, while the observer that did the measurement knows the state of the other component, they can only convey that information via regular, light speed, communication.

"If the new path is shorter than the other, then information can travel along it at a speed less than c, but still take less time than light going the long way."

If light can go through that wormhole, too, it technically wouldn't be FTL at all, would it? Otherwise, we already have FTL travel: point a laser at a mirror on the moon, step a meter aside, and wait for the light to finally get there.

Does this mean that N quantum computers can agree on the spin of an electron instantaneously, i.e., meaning that there's nothing like FLP impossibility result for distributed quantum computing? Or would that still imply violation of No-Communication theorem even if the observes can't exchange any information that way?

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