Researchers have successfully teleported wave packets of light | Hacker News Reader

Researchers have successfully teleported wave packets of light

abc.net.au

134 pointsUrgo53 comments

One thing that isn't clear in this article is whether they really teleportated it, meaning that they were able to transfer information instantaneously from point A to point B (which would go against Einstein's relativity law that states that nothing can go faster than the speed of light), or if they just transported a light beam from one point to another with regular means of communication.

It sounds more like it's the later case, and the word "teleportation" here is probably more a link bait than anything else.

And in any case, the title in the article is horrible: "Scientists teleport Schrodinger's cat"

Quantum teleportation does not allow for faster than light transmission of information.

"It does not transport the system itself, nor does it allow communication of information at superluminal (faster than light) speed." https://secure.wikimedia.org/wikipedia/en/wiki/Quantum_telep...

I doubt this is different.

Subspace radio allows for faster than light communication.

Magic, too.

This is not FTL no, that's still impossible and if they'd done -that- this would be a big deal indeed.

What this allows is simply transmitting "quantum information" from one place to another with any reliability at all, by packing it with classical information that helps accomplish that (being the macro-object/light packet).

http://en.wikipedia.org/wiki/No-teleportation_theorem explains why transmission of quantum information is difficult.

http://en.wikipedia.org/wiki/No-communication_theorem explains why quantum effects do not enable FTL transfer of classical information.

The speed limit of the universe isn't just some hypothesis waiting to be disproven. It can't be broken. It's impossible.

Never underestimate the capacity of humans to be wrong. Science is made from people being willing to admit they're wrong: the evidence for speed limits is compelling, but not absolute.

It would just mean our current model is screwed if we're wrong...

Assuming that the speed of light can be broken leads to hopelessly contradictory and paradoxical (truly paradoxical, not just counterintuitive) conclusions. It's not just some guess that scientists have made about how fast information can travel.

Scientific theories aren't reality - they are a model of reality and to be considered scientific a theory has to be refutable - if you can't conceive of experimental results that would disprove your theory then it's not really a scientific theory.

So every scientific theory is in a very real sense "waiting to be disproven".

We can know things. We know that no algorithm can determine whether or not arbitrary Turing machines will halt, because assuming the contrary leads to a contradiction. Similarly, no consistent axiomatic system powerful enough to express propositions of elementary arithmetic can be complete.

Neither the undecidability of the halting problem nor Gödel's first incompleteness theorem are "waiting to be disproven." Similarly, the speed limit of the universe, if assumed to be breakable, leads to all sorts of contradictions and true paradoxes. Note that I'm not saying that the entirety of some theory, be it special or general relativity, quantum theory, etc. are known truths.

Algorithms, being a sub-branch of mathematics, are logical constructs, which means they can be proved or disproved on a logical basis. Physics is a scientific model of reality which is based on experimental observations (mathematics is used as a descriptive language, but the underlying reality itself is not (as far as we know) based on logic), therefore any physical theory is not provable, only verifiable through experiment to some statistical probability of correctness. The current physics theory is backed by a huge amount of observations, so admittedly we can be pretty sure about much of the theory. But to say that we "know" is not correct.

It's explicitly clear in the article that this isn't "instantaneous" travel. As much as I hate the analogy, they basically were able to copy the box, the cat, the Geiger counter, and the radioactive trigger wholesale and transmit the copy somewhere else. Normally the process of copying would mean someone had to look in the box. This time they were able to copy the package without finding out if Heathcliff was alive or dead.

and the word "teleportation" here is probably more a link bait than anything else.

One thing I like about HN is that if I see a link that sounds too, umm, bait-y, I can just look at the comments here and avoid wasting my time (or at least getting excited without cause).

Quantum teleportation just means reproducing the entire quantum state of the system without physically transporting it. It's interesting to note that you can't do this without destroying the original (http://en.wikipedia.org/wiki/No-cloning_theorem).

It would appear that they did. The abstract of Lee et Al's report states:

"We report on the experimental quantum teleportation of strongly nonclassical wave packets of light. To perform this full quantum operation while preserving and retrieving the fragile nonclassicality of the input state, we have developed a broadband, zero-dispersion teleportation apparatus that works in conjunction with time-resolved state preparation equipment. Our approach brings within experimental reach a whole new set of hybrid protocols involving discrete- and continuous-variable techniques in quantum information processing for optical sciences." [1]

The abstract as a whole is a little beyond my knowledge of physics, but the way I read it seems to support that they did actually teleport - but in the quantum sense (ie they destroyed and recreated something in the same quantum state, not that they moved in instantaneously).

Another Science article in the same issue supports my reasoning "Such exotic quantum states can now be prepared in the lab, and even better, they can be teleported—that is, destroyed in one place and recreated in another one, as shown by Lee et al. (1) on page 330 of this issue." [2]

[1] - "Teleportation of Nonclassical Wave Packets of Light" - http://www.sciencemag.org/content/332/6027/330 (Science 15 April 2011: Vol. 332 no. 6027 pp. 313-314) [2] - "Make It Quantum and Continuous" - http://www.sciencemag.org/content/332/6027/313.full (Science 15 April 2011: Vol. 332 no. 6027 pp. 313-314)

"Teleportation" is a precise term in the field of quantum information; it wasn't the choice of the news article. Yes, the term was chosen to sound sexy, but it's not an unreasonable term for what it describes even if it can't quite live up to Star Trek.

A better word for non-quantum-physicists would be "transport" here. It's very difficult to move quantum bits from one place to another at all. The light beam is used to increase the reliability of that process.

This doesn't affect how -classical- information is transmitted or make it any better. It makes -quantum- information transmission reliable, which is actually pretty significant. This should allow for quantum computers of larger sizes than the super-tiny ones that have been created so far to actually work.

http://en.wikipedia.org/wiki/No-teleportation_theorem (why it is difficult to transmit quantum information)

http://en.wikipedia.org/wiki/Quantum_teleportation (what is being done in this experiment) What the breakthrough is is a way to do quantum telportation reliably -and- quickly (which had both been done before)

Why are people assuming that 'teleportation' means instantaneous travel?

To me, teleporting has always meant transferring the information that describes an object to another location, where the object is reproduced. This transfer of information occurs via light/radio waves or similar.

I hate to post what is nearly a "me too", but I'd also like to ask that question, with the clarification that I do not mean it as a rhetorical equivalent of "No, of course it's not instantaneous, duh", I am genuinely curious where the sheer confidence of the definition of "teleportation" as "instantaneous in violation of relativity" suddenly came from. Is there some scifi show on TV that I'm not watching that is promulgating this interpretation or something? I've seen the belief that entanglement can be used for FTL communication going back unto yea the very beginnings of the internet but this solid and shared definition of instantaneous is new to me vs. even the iteration of this whole argument I saw a few months ago. (Fringe maybe? Haven't started that yet.)

Not sure how anyone could of missed the whole teleport = instantaneous thing... Thankfully Wikipedia is here to save the day! http://en.wikipedia.org/wiki/List_of_fiction_containing_tele...

You just got played. It was done very well but nevertheless.

"Instantaneous", in that context, might not mean "faster than light". Communication via the internet is pretty much instantaneous, but it's not FTL...

I have had this conversation twice a year for the past ten to fifteen years. Something needs to have changed, because the conversation has changed in the way I cited. The vast bulk of those don't even address whether it's "instantaneous" in violation of lightspeed because they just ignore lightspeed entirely. You in fact seem to be reinforcing my point by the casual assumption that teleportation must be instantaneous-as-FTL by the very definition of the word, and thus the mere fact that the word is used proves your point (circularly, I might add), so let me ask you: Where did you get that idea? It's not the way the word has been defined for the past 50 years, it's a new mutation. Why do you think that? (And why would English have such a rigid, useless definition for a word like that?)

It may not be the word "teleportation" that triggers it. A lot of popular science fiction, e.g. the Commonwealth Saga, uses quantum entanglement as a plot device for instantaneous communication.

I'm assuming this due to modern fantasy borrowing the term from sci-fi (ie, "teleport" as a way to magically whisk someone/thing from one location to another instantaneously)... which popular culture has adopted wholesale.

I have a vague impression from articles read in the past that quantum entanglement could allow for a signal to be transferred over an arbitrarily large distance, instantaneously, because somehow a change at point A was 'magically' reflected at point B. I admit that this doesn't necessarily have anything to do with teleportation (I honestly don't understand their usage of the word).

By the way, a quick Google search shows that I am not alone in my thinking, and that I am wrong. :-)

This confusion comes up every time there's a popular article about quantum teleportation.

In a certain interpretation of the unambiguous mathematics, quantum teleportation does feature an instantaneous transfer of the quantum state. It's just that this state is useless for sending messages unless accompanied by a few bits of classical information. Since this classical info flows at less than the speed of light, there's no conflict with special relativity.

Teleportation is a misnomer here. Nothing is being teleported or transmitted rather information is being measured in two different locations simultaneously as if it were teleported. What I believe is that information is showing up in two different locations simultaneously. This term, entanglement, I think means that every quantum spin has an equal and opposite quantum spin at some other location that always exists. In other words, there's an opposite "thing" of our "thing" and when we adjust our "thing" we can now see or measure the opposite "thing" adjusting oppositely.

So what's the meaning here? I've been reading similar (to a non quantum physicist) stories for years and RTFA. What will this change about my life?

It sounds to me like it's an incremental improvement on existing technique, which the researchers are justifiably excited about, and through the Mighty Power of Mass-Market Science Journalism (TM) it becomes something that has never been done before, instead of it "merely" being done better than ever before. Photons have definitely been "teleported" before, as have individual atoms [1]. Though I scare-quote the word because it doesn't really precisely correspond to what people think of when they hear the term.

It's interesting, but it's not a breakthrough, nor does it herald any sort of advance in anything resembling Star Trek transporters, though to its credit I think this is the first Mass Market Science Journalism (TM) article on quantum teleportation I've seen that managed to avoid that faulty comparison, so points for that I guess.

[1]: http://www.livescience.com/7647-teleportation-milestone-achi... (which I would note fails the Star Trek test)

Minimum round trip time between San Francisco and Tokyo is about 60ms due to the speed of light, which means in practice FPS games are unplayable across the ocean.

If they manage to implement this shit, we'll be able to have FPS games hosted anywhere in the world!

This technology can not be used for faster-than-light communication. If it could, this would orders of magnitude larger news than it is.

Heh, I wish. Unfortunately, the word teleport here does not mean what everybody immediately thinks. Otherwise, this would mean sooo much more than lower latency gaming.

If we could actually break causality, playing games would be the last thing on our minds.

If causality is broken, how do you know it wasn't the first thing on our minds? :P

Quantum optics is outside my realm of expertise; to be honest my eyes kind of glaze over whenever these guys give a talk. The real life applications of this are not really teleportation in the "beam me up sense" but more along the lines of encryption.

If your transmission is based on quantum entangled photon states, it is physically impossible to eavesdrop without giving yourself away, since the act of eavesdropping 'collapses the quantum superposition' (like when you open the box with Schrodingers cat). They've actually already rolled out systems based on this technology in various places in the world, but there is a lot of work to improve bandwidth and so forth.

I won't say too much more as I'm well outside the field and will probably garble it.

Can anyone explain what quantum teleportation is? Wikipedia does not help, aside from assuring me that it is not what I thought it was:

Quantum teleportation, or entanglement-assisted teleportation, is a process by which a qubit (the basic unit of quantum information) can be transmitted exactly (in principle) from one location to another, without the qubit being transmitted through the intervening space. It is useful for quantum communication and computation. It does not transport the system itself, nor does it allow communication of information at superluminal (faster than light) speed. Neither does it concern rearranging the particles of a macroscopic object to copy the form of another object.

They entangled a q-bit with a packet of light, and then sent it from one place to another (presumably using fiber optic or something), without breaking entanglement.

This is important because it gets you the ability to route quantum information to different places.

Presumably a quantum bus in a computer or a quantum fiber-optic line.

I can see the marketing pamphlets now!

I found it best described as such: you put a white marble and a black marble in separate paper bags. You send one to a friend. As soon as you open the bag, you instantaneously know what color the other marble is. That doesn't mean you can instantaneously communicate with your friend.

I'll try to explain from what I understood in quantum physics class years ago.

When you're dealing with things on the quantum level, observing a particle affects it. Remember Schrodinger's cat? The cat is both dead and alive, until someone opens the box. The opening of the box gives the cat its new state of deadness or aliveness.

Quantum teleportation works through entangled particles. Entangled particles are, in some sense, the same particle in two places. An action on one entangled particle will instantly affect the other particle, including observation of the particle.

Suppose Alice and Bob share an entangled particle. Alice observes the particle on her end, collapsing it into one of four states. Which state it collapses into is and always will be completely random.

Bob's particle was instantaneously affected in one of four ways corresponding to those states. Trouble is, he doesn't know which way, and he can't do anything with his particle until he does.

Alice has to communicate to Bob in any regular way, through light, telephone or internet, what she observed on her end, so that Bob knows what exactly happened to his particle, and what to do with it.

So in this way, it really was instantaneous over a distance, but at the same time nothing useful happened faster than the speed of light.

Can someone please explain what the term "teleport" mean here? I'm not getting why this is an amazing scientific breakthrough (but I'd love to learn why it is).

If it doesn't mean information travelling instantaneously or faster than light, then did the reporter (or the scientist) put the word "teleport" in the title just so it's attention grabbing?!

Anyone found the DOI link yet? The explanation in the article is, I agree, awful, and I want to read what they actually did! If it was only moving a bit of information from RAM to a register (or the quantum equivalent) which it sounds like...then yea, no biggie.

And this is why science is hard to report on

Does this conflict with the notion of the speed of light being a universal maximum speed? If teleporting information causes bi-directional communication to be instant, aren't signals being propagated at faster than the speed of light?

It's not instantaneous; there's no conflict, no FTL to see here.

chinese dit it even over the air last year, distance - 16 km http://www.physorg.com/news193551675.html

so what's new?

I, uh, recognize the Hammond 1590D box. Do I get partial credit?

The damn cat was not both alive and dead simultaneously...

I have no idea what that experiment does but the pic is cool!

EDIT: The pic is not cool?

Downvotes probably due to people thinking that your comment adds nothing to the conversation, not necessarily disagreeing with you (I would think that the pic would be cooler if it were higher res; as it is, I can't make much sense of it).

http://www.abc.net.au/reslib/201104/r751650_6238699.jpg

reasonably high res

(a) So, what, those are optics they use to bounce the beam around, so they can get 10km of laser beam on a 5m bench?

(b) I can't look at that picture without thinking of Agatha's dingbots from Girl Genius. http://www.girlgeniusonline.com/comic.php?date=20091005

I think its cool.

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