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Researchers quantum teleport particle of light six kilometres

372 points by upen 10y ago

Someone1234 10y ago
Just to give a concept of how difficult this is: > “The challenge was to keep the photons’ arrival time synchronized to within 10 pico-seconds,” > “Since these detectors only work at temperatures less than one degree above absolute zero the equipment also included a compact cryostat,” said Tittel. The dark fiber seems like it was important for synchronizing the clocks. And while they claim this could be used for encryption keys, that is really a roundabout way of saying that very little information was actually transmitted/received, although the article doesn't say exactly how little. If this technology was refined, you'd just use this system to send secure messages without the need for an encryption key.
- jdmichal 10y ago
  > If this technology was refined, you'd just use this system to send secure messages without the need for an encryption key. As far as I know, I don't think that meshes with what actually happens. This has nothing to do with the message being secure; anyone with all the pieces could read the message. The important part is, since observation effects quantum state, the receiver can determine whether a third party observed the key. If the key matches, then there's a guarantee that it was not observed, and therefore is safe to use.
  - deleted 10y ago
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- Retr0spectrum 10y ago
  I'm really out of my depth on this topic, but I think I read that a theoretical cryptosystem could use the quantum state of a particle as a key, and perhaps this is what they are referencing.
atombath 10y ago
Awesome. So a quantum network would have the photon act as a data stream, in a way it would act like a physical security key. So with a lot of work, this would be amazing for 1:1 communications. But what if I want to send my dick pick to hundreds of people at once(1:100 distribution)? Is it possible to entangle one photon with multiple?
- jdmichal 10y ago
  Entanglement may be expanded to groups of particles. Also, I'd like to note that it's not necessarily that the communication is secure, but rather that third-party observation can be detected. That's why the discussion focuses on using this to send keys, and not messages themselves. https://news.ycombinator.com/item?id=12548798 https://news.ycombinator.com/item?id=12548798
3chelon 10y ago
10 picoseconds is "one millionth of one millionth of a second"? Damn it, I must have been misunderstanding engineering units all my life.
- hartator 10y ago
  Is it not? https://en.wikipedia.org/wiki/Picosecond https://en.wikipedia.org/wiki/Picosecond "or one millionth of one millionth of a second"
  - deleted 10y ago
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  - CocaKoala 10y ago
    Your link says that one picosecond is one millionth of one millionth of a second. The article itself says (or at least is written to imply) that ten picoseconds is one millionth of one millionth of a second. Since ten is not one, one of those two statements (and definitely not ten of those two statements) must be incorrect.
    - 24gttghh 10y ago
      I believe Wolfgang Tittel was simply defining a picosecond for the readers of the article.
      - CocaKoala 10y ago
        You're probably right. However, the article is written in a way which at the very least heavily implies something else. >“The challenge was to keep the photons’ arrival time synchronized to within 10 pico-seconds,” says Tittel. “That is one trillionth, or one millionth of one millionth of a second.”
        3chelon 10y ago
        Exactly. Which is how I read it. And how anyone would read it, I would think.
jdmichal 10y ago
I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/wiki/Superluminal_communication#Quantum_nonlocality https://en.wikipedia.org/wiki/Superluminal_communication#Qua... http://physics.stackexchange.com/a/203893 http://physics.stackexchange.com/a/203893 Given that, it seems like the touted benefit of using quantum entanglement here is in securing communications, since your measurements will no longer correlate if a third party is also measuring? At least, that's what I gathered.
- brazzledazzle 10y ago
  Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.
  - semi-extrinsic 10y ago
    This is a Hard Problem, to define what process is a "measurement" and what is not. But if we think about it very simply: a photon hitting a detector (or analog film strip) can be a measurement. Since this process converts quantum information to classical information (a digital or analog signal), we know that it must lose information. Only by making many measurements can we infer statistical properties of the entire quantum state. This is exactly what happens with the two-slit experiment. I personally subscribe to the "shut up and calculate" interpretation of QM (or perhaps the projection-valued operator approach when I'm feeling mathematical). The above intuition has served me well so far.
    - javajosh 10y ago
      > Since this process converts quantum information to classical information (a digital or analog signal), we know that it must lose information. Only by making many measurements can we infer statistical properties of the entire quantum state. This is exactly what happens with the two-slit experiment. Wow, I've never heard it explained that way. That's brilliant - did you come up with it? Interference patterns are the result of a huge number of individual photons interfering with each other at an enormous rate, and the result are laid out spatially...really lovely.
deleted 10y ago
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phkahler 10y ago
>> Researchers teleport particle of light six kilometres I'm sure they did nothing of the sort. At best they transferred an unknown state of a photon to another photon six kilometers away, then confirmed via measuring both.
- fizx 10y ago
  In other news, words can mean more than one thing.
  - Rooster61 10y ago
    True, but that doesn't mean you can use words that fundamentally change the meaning of the sentence and then pass it off as the same thing.
    - sowbug 10y ago
      I could care less.
      - spdustin 10y ago
        Couldn't?
        kbenson 10y ago
        At the risk of being too pedantic, that's the point. The incorrect phrasing is often used to mean the original thing, when the incorrect phrasing fundamentally changes the actual meaning of the sentence. That said, this is a chain of comments that skirts dangerously close to not-contributing IMO, since I'm not sure making cryptic comments that lead readers that don't happen to reach the right context sensitive interpretation to produce more comments asking about it aren't actually worse than a pure non sequitur, from a discussion point of view. Having a clever counter-example (as the GP does) is good. Leaving it unexplained and ambiguous is not.
      - ZoF 10y ago
Rooster61 10y ago
The title of the article, while probably not intentional clickbait, is incorrect. Only the quantum state of the photon was "teleported", not the photon itself. The original photon was in fact destroyed, and only the information about its state was transmitted.
- s_kilk 10y ago
  > The original photon was in fact destroyed, and only the information about its state was transmitted. Isn't that how teleportation works in, for example, Star Trek? https://www.youtube.com/watch?v=nQHBAdShgYI https://www.youtube.com/watch?v=nQHBAdShgYI
  - Rooster61 10y ago
    Funny you say that. When I read this for the first time, I had a flashback of Bones complaining about having his molecules scattered over space :)
- maggit 10y ago
  This is the exact meaning of quantum teleportation: https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation Changing the title to "Researchers quantum teleport particle..." would make it clearer. On the other hand, as far as I understand quantum mechanics, there is nothing about the "original" photon that was not teleported/transferred to the new location. It would be impossible to create an experiment that could conclude that the "target" photon was not in fact the original photon. When looking at it this way, it is not so unreasonable to call the process teleportation :)
  - turnip1979 10y ago
    Does the teleportation happen at the speed of light? Was inspired by Regetti's Startup School talk and have almost zero background :p
    - aparent 10y ago
jcoffland 10y ago
Teleportation is not possible. Quantum teleportation is the transmission of the exact state of a photon from one place to another. Still, even this happens at less than the speed of light. Otherwise it would violate causality. The media plays fast and loose with terminology either out of plain ignorance or the desire to sell a story.
- danharaj 10y ago
  There is nothing else about a photon that could be teleported.
- ctrl-j 10y ago
  > Teleportation is not possible. Quantum teleportation is the transmission of the exact state of a photon from one place to another. Still, even this happens at less than the speed of light. Otherwise it would violate causality. Maybe I'm remembering my QED special topics class incorrectly, but I thought the state teleportation is believed to be instant. The problem is to extract the state information, the transformation operators still need to be communicated. So you still have to get on the phone to tell your colleague across the planet what to do to see the entangled result. It's been years, so maybe I'm a little off on that? Causality also isn't a hard-and-fast law. We've just never seen it violated before. It's one of those physics problems that is really hard to find evidence to support or discredit it.
  - Skunkleton 10y ago
    So many advancements in physics have been the result of a smart person abandoning some "law".
    - jerf 10y ago
      Usually, in the process, discovering a deeper and stronger law. I understand the temptation to think that every "law" is just waiting to be broken, but I can easily read the same data and come to the opposite conclusion about the strength of our current "laws".
- 10y ago
kraftman 10y ago
>> Dark fibre, so named because of its composition — a single optical cable with no electronics or network equipment on the alignment — doesn’t interfere with quantum technology Isn't dark fibre either unlit capacity or leased fibres?
- nathanlied 10y ago
  It is, but I don't see why it can't have a different meaning for people on a different technical/theoretical area.
- devnull42 10y ago
  Or fibre that isnt on maps because it belongs to the government. At this point it has so many different meanings what is one more /s
- jomamaxx 10y ago
  Dark fibre I think is used simply to refer to fibre that's not being used at a given time. So I guess it can mean different things.
b3lvedere 10y ago
"if you’re a photon, you might want to keep reading." So, i stopped reading :)
- laksjd 10y ago
  It's just an if, not an iff ;)
itissid 10y ago
Correct me if this sounds noobish. So they have teleported state that has Information that can be decoded to bits and bytes(?) Forget about human teleportation for a sec, isn't this a big deal in a not so far future for telecommunication?
- tgb 10y ago
  Actually, they've done almost the reverse. To quantum teleport one qubit you have to transmit two classical bits, say by ethernet. In no way can this replace classical communication, it depends upon it.
- onli 10y ago
  They did nothing of the sort. Quantum physicists use words like teleport to say completely different things then what those words actually mean.
  - njwnought 10y ago
    This is correct. I'll quote the article here: "What happened is the instantaneous and disembodied transfer of the photon’s quantum state onto the remaining photon of the entangled pair, which is the one that remained six kilometres away at the university,” says Tittel". So teleport in this case doesn't really mean teleport, it just refers to the "teleportation" or transfer of a quantum state.
    - j1vms 10y ago
      I am not a career physicist, but have read much and thought deeply about these things. > So teleport in this case doesn't really mean teleport I would disagree with this statement. For all intents and purposes, the photon receiving the "transfer" is now indistinguishable from the photon that was transferred, before the event took place. That is to say, it has a completely identical quantum state following the transfer, and the "original" photon no longer has that "original" quantum state. They are only separate in space, and the transfer event took place at a defined "instant in time". It is is indeed ok to call this teleportation as (although this might seem odd in the practical sense) it is not possible to prove that the original photon was not teleported through space-time.
antouank 10y ago
Similar story from yesterday (BBC) https://news.ycombinator.com/item?id=12539375 https://news.ycombinator.com/item?id=12539375
d_theorist 10y ago
I had thought that quantum entanglement could not be used for communication because the state that is transmitted is random, and cannot be controlled at either end. But, there are quotes in this article to the contrary. e.g.: “Such a network will enable secure communication without having to worry about eavesdropping, and allow distant quantum computers to connect,” says Tittel. Was my understanding mistaken?
- alexmingoia 10y ago
  Somewhat related, China has launched the first quantum communications satellite which is meant to prevent eavesdropping using Quantum Key Distribution, http://www.nytimes.com/2016/08/17/world/asia/china-quantum-satellite-mozi.html?_r=0 http://www.nytimes.com/2016/08/17/world/asia/china-quantum-s...
- lmm 10y ago
  It isn't directly usable for communication, but you can use the shared random state as a one-time pad for provably-secure communication over nonsecure conventional channels.
  - d_theorist 10y ago
    Oh! Because both ends have access to the same random bits. Thanks.
- semi-extrinsic 10y ago
  I took a quantum optics course once. It's true what you say that entanglement can't be used to communicate (by itself), hence no problems with relativity, speed of light etc. This is known as the No-communication theorem: https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem But together with a conventional communications channel (e.g. radio signals), you can use quantum entanglement to create a secure communications channel. This combination is called quantum teleportation (as opposed to just quantum entanglement): https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation
fillskills 10y ago
This might sound like a very naive question but I am curious as to how the data was actually transmitted.
- aparent 10y ago
  Both ends of the experiment share entangled photons produced from a single source and sent both ways. The sender performs some operations and measurements on their two photons, i.e. the photon they wish to send, and their entangled photon. They then send the result of the measurements to the receiver (this can be done any normal way you can think of; for example over a classical network). The receiver does some operation on their entangled photon based on the results of the senders measurements. After these operations their entangled photon will be in the exact same state as the sent photon. So to answer your question, information is transmitted classically but that information would not be enough without the use of entanglement.
skywhopper 10y ago
Not satisfied with asking me to subscribe to their newsletter before I've even read one article, this site _also_ popped up a request that I allow them to send me desktop notifications. Do people actually fill these things out? Why does ScienceBulletin think I might even want these things?
- witty_username 10y ago
  This seems a new fad; I've seen this on other news websites.
- reduxive 10y ago
  Because obnoxious people will spam the form with emails that are not their own, as malicious behavior against acquaintences they detest. These ubiquitous subscribe forms provide a vector for inflating the size of mailing lists. Mailing lists with more addresses sell for real money, and sell well. It doesn't matter if the data is accurate. Only the perception of the data matters. The more addresses the better, the more datapoints per address, the higher the quality of data. The age and activity against the data matters. There are reputable companies that trade on these details and pay the salaries of expensive developers.
TheRealPomax 10y ago
Not quite as impressive when you know, and if you don't you should before opening this link, that "quantum teleportation" is not teleportation. It was a cool-sounding name at the time, but has nothing to do with sci-fi style teleportation: nothing disappears from one place and then shows up in another. "Quantum teleportation" is a process of information duplication using particles that already exist, and have been positioned such that there is enough distance between them that we can rule out direct interaction between them (that we know of given the current state of physics). Quantum teleportation is the process by which we then manipulate only the particles on one side of the distance divide, such that particles on the other side "end up" reflecting the same state that the ones we manipulated were. Although "ending up" is probably the wrong term, because we use particles in special states of which we already know they're entangled, then split them up (which does not cancel entanglement) and then we make use of their entanglement property: running an algorithm involving particles on one side should yield the exact same result as running the same algorithm on the other side, so a much more interesting algorithm is one that you run on one side in one way, and on the other in a different way, to effect a "data copy" without ever actually copying data (and very much without any kind of teleportation. The fact that you run your process with "the same particle" is the special part. Being able to even have two particles that are literally the same is a pretty bizarre bit of physics)
- aji 10y ago
  right, "quantum teleportation" is a woefully misleading name, however this is still an impressive advancement and quantum teleportation will play a key role in wide-area quantum information networks
  - radicaldreamer 10y ago
    This is probably also why SETI-like projects turn up nothing. It's likely that almost no advanced civilizations are using radio waves for communication.
    - ethanbond 10y ago
      I'm only a layman who's mildly interested in this, but this contradicts my understanding... Someone correct me if I'm wrong here. You can't communicate with quantum teleportation. It sends random "information" (not information at all), because you can't control how the quantum waveform collapses. So you have to collapse the waveform, create a key that encodes your collapsed form to the information you want to transmit, and then transmit that key slower than light i.e. with radio. I guess you could argue that since the keys themselves are also indistinguishable from noise, we wouldn't detect slower-than-light key transmission either, though.
sebringj 10y ago
Does modifying the state of one entangled particle then destroy the link between them? If it does, then how can you continually communicate without distance being a factor as you'll have to resupply? I hope it doesn't or there is some work around or I simply am completely asking the wrong question.
- jomamaxx 10y ago
  Yes, the observation destroys the entanglement. The communication does not really happen between the state that is 'teleported' - you still have to manually send the photons 6km or whatever. But - very crudely - you can pass information from one entangled particle to it's pair 6km away and observe the results. So, you still have to have a fiber or whatever. Also - because it's all probabilistic and you don't know for sure if it worked in any given instance, you still need another classical channel to communicate information about what was passed in the first place.
  - sebringj 10y ago
    Thank you for answering. I am still hopeful there will be another property found out about quantum behavior that will allow instant communication to be a reality.
mechazawa 10y ago
Forgive my ignorance as I'm a software engineer and not a physicist. But does this means that in the future FTL communication will be possible. Every time I work with networking one thing always springs to mind. That is that the speed of light is a limiting factor. Will this mean that in the future latency issues will be a thing of the past? http://www.stuartcheshire.org/rants/latency.html http://www.stuartcheshire.org/rants/latency.html
- daeken 10y ago
  Quantum teleportation can't be used to send data faster than the speed of light, more accurately understood here as the speed of causality. As far as I'm aware, there's really no hypothetical way to violate the speed of causality.
- roywiggins 10y ago
  You can't use entanglement to communicate. Quantum teleportation needs a classical channel to work. > https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem If you have superluminal communication, signals can travel into your subjective past, which means causality pretty much breaks down entirely. There's no theoretical reason why causality has to hold, but it would make life extremely "interesting"
  - pqhwan 10y ago
    There was a webcomic (or something like it) I saw a while ago that was about a single-buttoned gadget that could always predict whether you will press the button or not (don't remember the exact mechanism, but that was the jist). The story then went on about how the gadget would bring about humanity's collective philosophical collapse, because of its implications on the subject of free will. I imagine that what you're describing about superluminal communication could be used to make a gadget like this. I'm also wondering if anybody knows which webcomic I'm referring to. It'd be embarrassing if this turned out to be an XKCD number...
    - roywiggins 10y ago
reduxive 10y ago
Click bait. Deliberate use of hotword "teleport," to exploit bikeshedding debates. Cue endless discussions such as: What does teleport REALLY mean?
cryptarch 10y ago
I don't think I understand it right. My understanding is this: 1. send entangled bits to two separate locations A and B 2. determine their states (which will always be exactly opposite) on both sides 3. send data using classical means from A to B, xor'd with the quantum measurements 4. decrypt the data at B, with: data ^ quantum_measurements ^ 111111 (the last step being "invert all bits and ^ representing xor). If that's it, how is this much better than sending block of identical entropy to A and B, and using a OTP? Theoretial tamper-proofness?
- roywiggins 10y ago
  My understanding is that it's snooping-evident, at least in theory. If someone takes a peek at the entangled bits in transit, the entanglement will be broken and when A and B compare notes, their states will no longer be correlated. This is good for key distribution because if someone snoops a key, you know the key is compromised and throw it away. If you have a secure way to distribute your OTP I'm not sure there'd be a benefit to using quantum teleportation at all.
  - cryptarch 10y ago
    But if you have a secure way of getting your quantum bits to Bob, couldn't you get your OTP there in the same way? I mean, yes, you could detect it if your stream of entangled bits is intercepted while it is going, but you couldn't detect it if it was intercepted from the get go and MITM'd.
    - dsacco 10y ago
      >>But if you have a secure way of getting your quantum bits to Bob, couldn't you get your OTP there in the same way? No, because you do not choose the information to be verified on either side. You're not choosing a key and "encoding" it into "quantum bits", you're measuring the quantum state of two entangled particles. If the quantum state matches, you have provably secure transmission. If the transmission were intercepted, the act of intercepting it would cause the measurement verification to fail due to the observer effect. The parties would be able to see that the key was intercepted because the particles were prematurely disentangled. This is quantum key distribution, which is a subset of (and often misleadingly conflated with) quantum cryptography. It is not possible to use quantum cryptography to send provably secure arbitrary data of your choosing, it's only possible to generate and distribute provably secure keys and use those for classical cryptographic communication. The reason why it's important to call it quantum key distribution is because it makes it clearer that this only solves one problem in a greater cryptosystem. Key distribution is a significant problem in cryptography, and provably secure key distribution is a great leap forward, but it's not the only problem.
l3m0ndr0p 10y ago
Meanwhile, in the 8th dimension, the Red Lectroids are planning their escape.
tempestn 10y ago
There appears to be a great deal of conflation in many of these comments between quantum entanglement and quantum teleportation. Quantum teleportation makes use of entanglement, but is a different thing entirely. In short, quantum entanglement is an effect that causes two quantum particles to share state instantaneously over arbitrary distances. It can not be used to transmit information faster than the speed of light, essentially because while it is possible to manipulate the particle at one end, it is not possible to arbitrarily set it to a chosen state (and as described fully in the no communication theorem)[1]. Quantum teleportation is a way to transmit quantum information, ie the quantum state of a 'qubit', using both quantum entanglement and a classical communication channel. Because classical communication is required, no faster than light communication is possible. However, quantum teleportation is necessary if you want to transmit quantum information. To very briefly sum up how it works, you start with a qubit whose state you want to transmit, along with two entangled particles, and a 'receiving' qubit that will receive the state of the sending qubit. Through an interaction between the sending qubit and the entangled particle on the sending side, the quantum state of the entangled particles is set to one of four possibilities. Which of the four possibilities resulted is sent via the classical communication channel from sending to receiving end. The receiving end then uses that information, along with the receiving-end entangled particle, to manipulate the receiving qubit into the identical state as the sending qubit, thereby 'teleporting' that state from sending to receiving end. The Wikipedia article has a more thorough layman's description, as well as the underlying math[2]. Caveat: I'm an engineer, not a physicist, so I may have made a mistake here as well, but the main take-away is that quantum teleportation is not the same thing as quantum entanglement, and its purpose is not FTL communication, but rather communication of quantum states. [1] https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem [2] https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation
cody3222 10y ago
The Uber killer
intrasight 10y ago
There are no particles - only waves. Particles are, in a sense, observation artifacts. Once you grok that, action at a distance doesn't seem so strange.
deleted 10y ago
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rdlecler1 10y ago
Is it reasonable to assume that more advanced civilizations would use technology like this for communication instead of radio transmission meaning that SETI is doomed and the Fermi Paradox may be no paradox at all?
beothorn 10y ago
For anyone interested, there is a great video by the PBS space time channel explaining quantum entanglement here https://www.youtube.com/watch?v=tafGL02EUOA https://www.youtube.com/watch?v=tafGL02EUOA The thing is, although the quantum state of the photom collapses instantaneously on both entangled photons, we can't manipulate at which state the photon will collapse, and so, we can't really send information using quantum entanglement. We can't also confirm the entanglement until we can compare both measurement results or else we could send information from the future as in the quantum eraser experiment https://www.youtube.com/watch?v=2Uzytrooz44 https://www.youtube.com/watch?v=2Uzytrooz44 Edit: formatting and typos

372 points by upen 10y ago

Just to give a concept of how difficult this is: > “The challenge was to keep the photons’ arrival time synchronized to within 10 pico-seconds,” > “Since these detectors only work at temperatures less than one degree above absolute zero the equipment also included a compact cryostat,” said Tittel. The dark fiber seems like it was important for synchronizing the clocks. And while they claim this could be used for encryption keys, that is really a roundabout way of saying that very little information was actually transmitted/received, although the article doesn't say exactly how little. If this technology was refined, you'd just use this system to send secure messages without the need for an encryption key.

jdmichal 10y ago
> If this technology was refined, you'd just use this system to send secure messages without the need for an encryption key. As far as I know, I don't think that meshes with what actually happens. This has nothing to do with the message being secure; anyone with all the pieces could read the message. The important part is, since observation effects quantum state, the receiver can determine whether a third party observed the key. If the key matches, then there's a guarantee that it was not observed, and therefore is safe to use.
- deleted 10y ago
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Retr0spectrum 10y ago
I'm really out of my depth on this topic, but I think I read that a theoretical cryptosystem could use the quantum state of a particle as a key, and perhaps this is what they are referencing.

atombath 10y ago

Awesome. So a quantum network would have the photon act as a data stream, in a way it would act like a physical security key. So with a lot of work, this would be amazing for 1:1 communications. But what if I want to send my dick pick to hundreds of people at once(1:100 distribution)? Is it possible to entangle one photon with multiple?

jdmichal 10y ago
Entanglement may be expanded to groups of particles. Also, I'd like to note that it's not necessarily that the communication is secure, but rather that third-party observation can be detected. That's why the discussion focuses on using this to send keys, and not messages themselves. https://news.ycombinator.com/item?id=12548798 https://news.ycombinator.com/item?id=12548798

3chelon 10y ago

10 picoseconds is "one millionth of one millionth of a second"? Damn it, I must have been misunderstanding engineering units all my life.

hartator 10y ago
Is it not? https://en.wikipedia.org/wiki/Picosecond https://en.wikipedia.org/wiki/Picosecond "or one millionth of one millionth of a second"
- deleted 10y ago
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- CocaKoala 10y ago
  Your link says that one picosecond is one millionth of one millionth of a second. The article itself says (or at least is written to imply) that ten picoseconds is one millionth of one millionth of a second. Since ten is not one, one of those two statements (and definitely not ten of those two statements) must be incorrect.
  - 24gttghh 10y ago
    I believe Wolfgang Tittel was simply defining a picosecond for the readers of the article.
    - CocaKoala 10y ago
      You're probably right. However, the article is written in a way which at the very least heavily implies something else. >“The challenge was to keep the photons’ arrival time synchronized to within 10 pico-seconds,” says Tittel. “That is one trillionth, or one millionth of one millionth of a second.”
      - 3chelon 10y ago
        Exactly. Which is how I read it. And how anyone would read it, I would think.

jdmichal 10y ago

I posted this in a duplicate thread: For those thinking that this is a step towards faster-than-light (FTL) communication: As far as I know it's fairly certain that quantum entanglement will not allow for FTL communication. Basic principle is that while measurements between both sides will be correlated, it's not possible to tell how they are correlated until both sides compare measurements. https://en.wikipedia.org/wiki/Superluminal_communication#Quantum_nonlocality https://en.wikipedia.org/wiki/Superluminal_communication#Qua... http://physics.stackexchange.com/a/203893 http://physics.stackexchange.com/a/203893 Given that, it seems like the touted benefit of using quantum entanglement here is in securing communications, since your measurements will no longer correlate if a third party is also measuring? At least, that's what I gathered.

brazzledazzle 10y ago
Is "measurement" or "observation" a simplified term for a complex process? It can't be as simple as a human "looking" at something since there's nothing special about humans (that I know of). I really wish I had the time and capability to understood how quantum entanglement really works. It seems a lot like magic if you take the layman explanations at face value.
- semi-extrinsic 10y ago
  This is a Hard Problem, to define what process is a "measurement" and what is not. But if we think about it very simply: a photon hitting a detector (or analog film strip) can be a measurement. Since this process converts quantum information to classical information (a digital or analog signal), we know that it must lose information. Only by making many measurements can we infer statistical properties of the entire quantum state. This is exactly what happens with the two-slit experiment. I personally subscribe to the "shut up and calculate" interpretation of QM (or perhaps the projection-valued operator approach when I'm feeling mathematical). The above intuition has served me well so far.
  - javajosh 10y ago
    > Since this process converts quantum information to classical information (a digital or analog signal), we know that it must lose information. Only by making many measurements can we infer statistical properties of the entire quantum state. This is exactly what happens with the two-slit experiment. Wow, I've never heard it explained that way. That's brilliant - did you come up with it? Interference patterns are the result of a huge number of individual photons interfering with each other at an enormous rate, and the result are laid out spatially...really lovely.

deleted 10y ago

[deleted]

phkahler 10y ago

>> Researchers teleport particle of light six kilometres I'm sure they did nothing of the sort. At best they transferred an unknown state of a photon to another photon six kilometers away, then confirmed via measuring both.

fizx 10y ago
In other news, words can mean more than one thing.
- Rooster61 10y ago
  True, but that doesn't mean you can use words that fundamentally change the meaning of the sentence and then pass it off as the same thing.
  - sowbug 10y ago
    I could care less.
    - spdustin 10y ago
      Couldn't?
      - kbenson 10y ago
        At the risk of being too pedantic, that's the point. The incorrect phrasing is often used to mean the original thing, when the incorrect phrasing fundamentally changes the actual meaning of the sentence. That said, this is a chain of comments that skirts dangerously close to not-contributing IMO, since I'm not sure making cryptic comments that lead readers that don't happen to reach the right context sensitive interpretation to produce more comments asking about it aren't actually worse than a pure non sequitur, from a discussion point of view. Having a clever counter-example (as the GP does) is good. Leaving it unexplained and ambiguous is not.
    - ZoF 10y ago

Rooster61 10y ago

The title of the article, while probably not intentional clickbait, is incorrect. Only the quantum state of the photon was "teleported", not the photon itself. The original photon was in fact destroyed, and only the information about its state was transmitted.

s_kilk 10y ago
> The original photon was in fact destroyed, and only the information about its state was transmitted. Isn't that how teleportation works in, for example, Star Trek? https://www.youtube.com/watch?v=nQHBAdShgYI https://www.youtube.com/watch?v=nQHBAdShgYI
- Rooster61 10y ago
  Funny you say that. When I read this for the first time, I had a flashback of Bones complaining about having his molecules scattered over space :)
maggit 10y ago
This is the exact meaning of quantum teleportation: https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation Changing the title to "Researchers quantum teleport particle..." would make it clearer. On the other hand, as far as I understand quantum mechanics, there is nothing about the "original" photon that was not teleported/transferred to the new location. It would be impossible to create an experiment that could conclude that the "target" photon was not in fact the original photon. When looking at it this way, it is not so unreasonable to call the process teleportation :)
- turnip1979 10y ago
  Does the teleportation happen at the speed of light? Was inspired by Regetti's Startup School talk and have almost zero background :p
  - aparent 10y ago

jcoffland 10y ago

Teleportation is not possible. Quantum teleportation is the transmission of the exact state of a photon from one place to another. Still, even this happens at less than the speed of light. Otherwise it would violate causality. The media plays fast and loose with terminology either out of plain ignorance or the desire to sell a story.

danharaj 10y ago
There is nothing else about a photon that could be teleported.
ctrl-j 10y ago
> Teleportation is not possible. Quantum teleportation is the transmission of the exact state of a photon from one place to another. Still, even this happens at less than the speed of light. Otherwise it would violate causality. Maybe I'm remembering my QED special topics class incorrectly, but I thought the state teleportation is believed to be instant. The problem is to extract the state information, the transformation operators still need to be communicated. So you still have to get on the phone to tell your colleague across the planet what to do to see the entangled result. It's been years, so maybe I'm a little off on that? Causality also isn't a hard-and-fast law. We've just never seen it violated before. It's one of those physics problems that is really hard to find evidence to support or discredit it.
- Skunkleton 10y ago
  So many advancements in physics have been the result of a smart person abandoning some "law".
  - jerf 10y ago
    Usually, in the process, discovering a deeper and stronger law. I understand the temptation to think that every "law" is just waiting to be broken, but I can easily read the same data and come to the opposite conclusion about the strength of our current "laws".
10y ago

kraftman 10y ago

>> Dark fibre, so named because of its composition — a single optical cable with no electronics or network equipment on the alignment — doesn’t interfere with quantum technology Isn't dark fibre either unlit capacity or leased fibres?

nathanlied 10y ago
It is, but I don't see why it can't have a different meaning for people on a different technical/theoretical area.
devnull42 10y ago
Or fibre that isnt on maps because it belongs to the government. At this point it has so many different meanings what is one more /s
jomamaxx 10y ago
Dark fibre I think is used simply to refer to fibre that's not being used at a given time. So I guess it can mean different things.

b3lvedere 10y ago

"if you’re a photon, you might want to keep reading." So, i stopped reading :)

laksjd 10y ago
It's just an if, not an iff ;)

itissid 10y ago

Correct me if this sounds noobish. So they have teleported state that has Information that can be decoded to bits and bytes(?) Forget about human teleportation for a sec, isn't this a big deal in a not so far future for telecommunication?

tgb 10y ago
Actually, they've done almost the reverse. To quantum teleport one qubit you have to transmit two classical bits, say by ethernet. In no way can this replace classical communication, it depends upon it.
onli 10y ago
They did nothing of the sort. Quantum physicists use words like teleport to say completely different things then what those words actually mean.
- njwnought 10y ago
  This is correct. I'll quote the article here: "What happened is the instantaneous and disembodied transfer of the photon’s quantum state onto the remaining photon of the entangled pair, which is the one that remained six kilometres away at the university,” says Tittel". So teleport in this case doesn't really mean teleport, it just refers to the "teleportation" or transfer of a quantum state.
  - j1vms 10y ago
    I am not a career physicist, but have read much and thought deeply about these things. > So teleport in this case doesn't really mean teleport I would disagree with this statement. For all intents and purposes, the photon receiving the "transfer" is now indistinguishable from the photon that was transferred, before the event took place. That is to say, it has a completely identical quantum state following the transfer, and the "original" photon no longer has that "original" quantum state. They are only separate in space, and the transfer event took place at a defined "instant in time". It is is indeed ok to call this teleportation as (although this might seem odd in the practical sense) it is not possible to prove that the original photon was not teleported through space-time.

antouank 10y ago

Similar story from yesterday (BBC) https://news.ycombinator.com/item?id=12539375 https://news.ycombinator.com/item?id=12539375

d_theorist 10y ago

I had thought that quantum entanglement could not be used for communication because the state that is transmitted is random, and cannot be controlled at either end. But, there are quotes in this article to the contrary. e.g.: “Such a network will enable secure communication without having to worry about eavesdropping, and allow distant quantum computers to connect,” says Tittel. Was my understanding mistaken?

alexmingoia 10y ago
Somewhat related, China has launched the first quantum communications satellite which is meant to prevent eavesdropping using Quantum Key Distribution, http://www.nytimes.com/2016/08/17/world/asia/china-quantum-satellite-mozi.html?_r=0 http://www.nytimes.com/2016/08/17/world/asia/china-quantum-s...
lmm 10y ago
It isn't directly usable for communication, but you can use the shared random state as a one-time pad for provably-secure communication over nonsecure conventional channels.
- d_theorist 10y ago
  Oh! Because both ends have access to the same random bits. Thanks.
semi-extrinsic 10y ago
I took a quantum optics course once. It's true what you say that entanglement can't be used to communicate (by itself), hence no problems with relativity, speed of light etc. This is known as the No-communication theorem: https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem But together with a conventional communications channel (e.g. radio signals), you can use quantum entanglement to create a secure communications channel. This combination is called quantum teleportation (as opposed to just quantum entanglement): https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation

fillskills 10y ago

This might sound like a very naive question but I am curious as to how the data was actually transmitted.

aparent 10y ago
Both ends of the experiment share entangled photons produced from a single source and sent both ways. The sender performs some operations and measurements on their two photons, i.e. the photon they wish to send, and their entangled photon. They then send the result of the measurements to the receiver (this can be done any normal way you can think of; for example over a classical network). The receiver does some operation on their entangled photon based on the results of the senders measurements. After these operations their entangled photon will be in the exact same state as the sent photon. So to answer your question, information is transmitted classically but that information would not be enough without the use of entanglement.

skywhopper 10y ago

Not satisfied with asking me to subscribe to their newsletter before I've even read one article, this site _also_ popped up a request that I allow them to send me desktop notifications. Do people actually fill these things out? Why does ScienceBulletin think I might even want these things?

witty_username 10y ago
This seems a new fad; I've seen this on other news websites.
reduxive 10y ago
Because obnoxious people will spam the form with emails that are not their own, as malicious behavior against acquaintences they detest. These ubiquitous subscribe forms provide a vector for inflating the size of mailing lists. Mailing lists with more addresses sell for real money, and sell well. It doesn't matter if the data is accurate. Only the perception of the data matters. The more addresses the better, the more datapoints per address, the higher the quality of data. The age and activity against the data matters. There are reputable companies that trade on these details and pay the salaries of expensive developers.

TheRealPomax 10y ago

Not quite as impressive when you know, and if you don't you should before opening this link, that "quantum teleportation" is not teleportation. It was a cool-sounding name at the time, but has nothing to do with sci-fi style teleportation: nothing disappears from one place and then shows up in another. "Quantum teleportation" is a process of information duplication using particles that already exist, and have been positioned such that there is enough distance between them that we can rule out direct interaction between them (that we know of given the current state of physics). Quantum teleportation is the process by which we then manipulate only the particles on one side of the distance divide, such that particles on the other side "end up" reflecting the same state that the ones we manipulated were. Although "ending up" is probably the wrong term, because we use particles in special states of which we already know they're entangled, then split them up (which does not cancel entanglement) and then we make use of their entanglement property: running an algorithm involving particles on one side should yield the exact same result as running the same algorithm on the other side, so a much more interesting algorithm is one that you run on one side in one way, and on the other in a different way, to effect a "data copy" without ever actually copying data (and very much without any kind of teleportation. The fact that you run your process with "the same particle" is the special part. Being able to even have two particles that are literally the same is a pretty bizarre bit of physics)

aji 10y ago
right, "quantum teleportation" is a woefully misleading name, however this is still an impressive advancement and quantum teleportation will play a key role in wide-area quantum information networks
- radicaldreamer 10y ago
  This is probably also why SETI-like projects turn up nothing. It's likely that almost no advanced civilizations are using radio waves for communication.
  - ethanbond 10y ago
    I'm only a layman who's mildly interested in this, but this contradicts my understanding... Someone correct me if I'm wrong here. You can't communicate with quantum teleportation. It sends random "information" (not information at all), because you can't control how the quantum waveform collapses. So you have to collapse the waveform, create a key that encodes your collapsed form to the information you want to transmit, and then transmit that key slower than light i.e. with radio. I guess you could argue that since the keys themselves are also indistinguishable from noise, we wouldn't detect slower-than-light key transmission either, though.

sebringj 10y ago

Does modifying the state of one entangled particle then destroy the link between them? If it does, then how can you continually communicate without distance being a factor as you'll have to resupply? I hope it doesn't or there is some work around or I simply am completely asking the wrong question.

jomamaxx 10y ago
Yes, the observation destroys the entanglement. The communication does not really happen between the state that is 'teleported' - you still have to manually send the photons 6km or whatever. But - very crudely - you can pass information from one entangled particle to it's pair 6km away and observe the results. So, you still have to have a fiber or whatever. Also - because it's all probabilistic and you don't know for sure if it worked in any given instance, you still need another classical channel to communicate information about what was passed in the first place.
- sebringj 10y ago
  Thank you for answering. I am still hopeful there will be another property found out about quantum behavior that will allow instant communication to be a reality.

mechazawa 10y ago

Forgive my ignorance as I'm a software engineer and not a physicist. But does this means that in the future FTL communication will be possible. Every time I work with networking one thing always springs to mind. That is that the speed of light is a limiting factor. Will this mean that in the future latency issues will be a thing of the past? http://www.stuartcheshire.org/rants/latency.html http://www.stuartcheshire.org/rants/latency.html

daeken 10y ago
Quantum teleportation can't be used to send data faster than the speed of light, more accurately understood here as the speed of causality. As far as I'm aware, there's really no hypothetical way to violate the speed of causality.
roywiggins 10y ago
You can't use entanglement to communicate. Quantum teleportation needs a classical channel to work. > https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem If you have superluminal communication, signals can travel into your subjective past, which means causality pretty much breaks down entirely. There's no theoretical reason why causality has to hold, but it would make life extremely "interesting"
- pqhwan 10y ago
  There was a webcomic (or something like it) I saw a while ago that was about a single-buttoned gadget that could always predict whether you will press the button or not (don't remember the exact mechanism, but that was the jist). The story then went on about how the gadget would bring about humanity's collective philosophical collapse, because of its implications on the subject of free will. I imagine that what you're describing about superluminal communication could be used to make a gadget like this. I'm also wondering if anybody knows which webcomic I'm referring to. It'd be embarrassing if this turned out to be an XKCD number...
  - roywiggins 10y ago

reduxive 10y ago

Click bait. Deliberate use of hotword "teleport," to exploit bikeshedding debates. Cue endless discussions such as: What does teleport REALLY mean?

cryptarch 10y ago

I don't think I understand it right. My understanding is this: 1. send entangled bits to two separate locations A and B 2. determine their states (which will always be exactly opposite) on both sides 3. send data using classical means from A to B, xor'd with the quantum measurements 4. decrypt the data at B, with: data ^ quantum_measurements ^ 111111 (the last step being "invert all bits and ^ representing xor). If that's it, how is this much better than sending block of identical entropy to A and B, and using a OTP? Theoretial tamper-proofness?

roywiggins 10y ago
My understanding is that it's snooping-evident, at least in theory. If someone takes a peek at the entangled bits in transit, the entanglement will be broken and when A and B compare notes, their states will no longer be correlated. This is good for key distribution because if someone snoops a key, you know the key is compromised and throw it away. If you have a secure way to distribute your OTP I'm not sure there'd be a benefit to using quantum teleportation at all.
- cryptarch 10y ago
  But if you have a secure way of getting your quantum bits to Bob, couldn't you get your OTP there in the same way? I mean, yes, you could detect it if your stream of entangled bits is intercepted while it is going, but you couldn't detect it if it was intercepted from the get go and MITM'd.
  - dsacco 10y ago
    >>But if you have a secure way of getting your quantum bits to Bob, couldn't you get your OTP there in the same way? No, because you do not choose the information to be verified on either side. You're not choosing a key and "encoding" it into "quantum bits", you're measuring the quantum state of two entangled particles. If the quantum state matches, you have provably secure transmission. If the transmission were intercepted, the act of intercepting it would cause the measurement verification to fail due to the observer effect. The parties would be able to see that the key was intercepted because the particles were prematurely disentangled. This is quantum key distribution, which is a subset of (and often misleadingly conflated with) quantum cryptography. It is not possible to use quantum cryptography to send provably secure arbitrary data of your choosing, it's only possible to generate and distribute provably secure keys and use those for classical cryptographic communication. The reason why it's important to call it quantum key distribution is because it makes it clearer that this only solves one problem in a greater cryptosystem. Key distribution is a significant problem in cryptography, and provably secure key distribution is a great leap forward, but it's not the only problem.

l3m0ndr0p 10y ago

Meanwhile, in the 8th dimension, the Red Lectroids are planning their escape.

tempestn 10y ago

There appears to be a great deal of conflation in many of these comments between quantum entanglement and quantum teleportation. Quantum teleportation makes use of entanglement, but is a different thing entirely. In short, quantum entanglement is an effect that causes two quantum particles to share state instantaneously over arbitrary distances. It can not be used to transmit information faster than the speed of light, essentially because while it is possible to manipulate the particle at one end, it is not possible to arbitrarily set it to a chosen state (and as described fully in the no communication theorem)[1]. Quantum teleportation is a way to transmit quantum information, ie the quantum state of a 'qubit', using both quantum entanglement and a classical communication channel. Because classical communication is required, no faster than light communication is possible. However, quantum teleportation is necessary if you want to transmit quantum information. To very briefly sum up how it works, you start with a qubit whose state you want to transmit, along with two entangled particles, and a 'receiving' qubit that will receive the state of the sending qubit. Through an interaction between the sending qubit and the entangled particle on the sending side, the quantum state of the entangled particles is set to one of four possibilities. Which of the four possibilities resulted is sent via the classical communication channel from sending to receiving end. The receiving end then uses that information, along with the receiving-end entangled particle, to manipulate the receiving qubit into the identical state as the sending qubit, thereby 'teleporting' that state from sending to receiving end. The Wikipedia article has a more thorough layman's description, as well as the underlying math[2]. Caveat: I'm an engineer, not a physicist, so I may have made a mistake here as well, but the main take-away is that quantum teleportation is not the same thing as quantum entanglement, and its purpose is not FTL communication, but rather communication of quantum states. [1] https://en.wikipedia.org/wiki/No-communication_theorem https://en.wikipedia.org/wiki/No-communication_theorem [2] https://en.wikipedia.org/wiki/Quantum_teleportation https://en.wikipedia.org/wiki/Quantum_teleportation

cody3222 10y ago

The Uber killer

intrasight 10y ago

There are no particles - only waves. Particles are, in a sense, observation artifacts. Once you grok that, action at a distance doesn't seem so strange.

deleted 10y ago

[deleted]

rdlecler1 10y ago

Is it reasonable to assume that more advanced civilizations would use technology like this for communication instead of radio transmission meaning that SETI is doomed and the Fermi Paradox may be no paradox at all?

beothorn 10y ago

For anyone interested, there is a great video by the PBS space time channel explaining quantum entanglement here https://www.youtube.com/watch?v=tafGL02EUOA https://www.youtube.com/watch?v=tafGL02EUOA The thing is, although the quantum state of the photom collapses instantaneously on both entangled photons, we can't manipulate at which state the photon will collapse, and so, we can't really send information using quantum entanglement. We can't also confirm the entanglement until we can compare both measurement results or else we could send information from the future as in the quantum eraser experiment https://www.youtube.com/watch?v=2Uzytrooz44 https://www.youtube.com/watch?v=2Uzytrooz44 Edit: formatting and typos