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Communications Canada Encryption Technology Science

Quantum Teleportation Sends Information 143 Kilometers 333

SchrodingerZ writes "Scientists from around the world have collaborated to achieve quantum teleportation over 143 kilometers in free space. Quantum information was sent between the Canary Islands of La Palma and Tenerife. Quantum teleportation is not how it is made out in Star Trek, though. Instead of sending an object (in this case a photon) from one location to another; the information of its quantum state is sent, making a photon on the other end look identical to the original. 'Teleportation across 143 kilometres is a crucial milestone in this research, since that is roughly the minimum distance between the ground and orbiting satellites.' It is the hope of the research team that this experiment will lead to commercial use of quantum teleportation to interact with satellites and ground stations. This will increase the efficiency of satellite communication and help with the expansion of quantum internet usage. The full paper on the experiment can be found [note: abstract only, full article paywalled] in the journal Nature."
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Quantum Teleportation Sends Information 143 Kilometers

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  • If I recall..... (Score:3, Insightful)

    by Sparticus789 ( 2625955 ) on Thursday September 06, 2012 @09:31AM (#41246879) Journal

    Isn't this how the Ansible from Ender's Game works? Two particles made to be in the exact same state, despite being physically separated? Too bad we couldn't have put this type of technology on Voyager 1 and 2.

    • by arth1 ( 260657 )

      Isn't this how the Ansible from Ender's Game works? Two particles made to be in the exact same state, despite being physically separated? Too bad we couldn't have put this type of technology on Voyager 1 and 2.

      No, this particular form of "teleportation" also requires sending photons between the two sites - not storing particles for later usage.

    • No, because the uncertainty principle still applies. Entangled particles are in an identical state, but that state is still probabilistic. To get any information out of it you have to measure it, and measurements on the two particles can come out different.

      • Re:If I recall..... (Score:4, Informative)

        by tnk1 ( 899206 ) on Thursday September 06, 2012 @01:42PM (#41250669)

        Yes and no.

        Probability is very important, but it is not the measurement, or at least not the initial measurements, which are the issue.

        The measurements on the particles will actually be the spookily transmitted values that you would expect. If person A observes his particle and locks in a state, the particle of person B will instantly take on the mirror or opposite of what person A has measured. Until entanglement is broken, particle B will remain in that state for person B to discover almost at their leisure. So, you *can* measure two particles and get the same/mirror answer... but only once per particle.

        Or in other words, if Person A observes a living Schrodinger's Cat in his box, Person B will get a dead one in his entangled box instantly, which will be there for him to see when he opens the box. It will not go back to being uncertain until the box is opened and then closed again. Person B does get the opportunity to see the state of his particle as changed by entanglement.

        So what is the problem? Sounds like this is faster than light. And it is. However, Relativity does not state that nothing can happen faster than light, only that *information* cannot be transmitted faster than light. The problem is entanglement does not actually create a channel for passing information by itself.

        For information to be passed one side must use a channel to send a message to the other. With entanglement you will have "sent" a state, but the other side has no way of knowing you actually sent a message, which in turn means that information is not passed.

        Remember, collapsing the probabilities and killing/not killing a cat can be done by *either side*. That means that if you open your box and find a living cat, it could mean that your partner earlier opened his box and found his cat was dead (and is attempting to send you a message). Alternately, it might mean he hadn't gotten around to opening his box yet and you opened first, making you are responsible for killing his cat which he may soon discover (you monster).

        This is *not* insurmountable normally. If you could, say, ensure that you always kill the cat in your box when you are sending a message, then I could use frequency analysis or some other algorithm on all of my living cat results because I know that only living cats can be message data. There would still be a ratio of noise to the signal due to the ever present possibility that I am killing his cat on the other side by looking before he does, but you should be able to wring data out of it. You would, of course, need multiple entangled boxes for this, but other than representing mass cat murder, this is not a major problem.

        Unfortunately, this is where the Uncertainty Principle checkmates us. When you open a box, it is always completely random what you get. You can't force a result or know ahead of time what you will send, so pre-arranging to only accept one result is pointless. Even the smallest attempt to alter the box before opening it in a manner that would make the result even slightly more predictable counts as a measurement and trips the entanglement effect. Then when you go to look in the box afterward, you are simply looking at particle that is no longer entangled. In effect, altering the box in any useful way is the same thing as opening it.

        So, to actually send a decipherable message, you need a classical, slower than light channel to decipher every bit of information you send via entangled particles. While it is technically true that your actual bits arrived faster than light, the information is 100% indecipherable until you get the decoder for each bit at light speed, and so there is no way to disseminate actual information faster than light in this way.

    • That's just good old quantum entanglement what the article is describing is taking one of the entangled particles and teleporting it 143km which could put the particle into orbit (just). More info >>
    • by Greyfox ( 87712 ) on Thursday September 06, 2012 @10:23AM (#41247573) Homepage Journal
      No! Quantum entanglement is more like herpes! Lets say I give you herpes! Now we share the herpes state. Later on the next person you want to have sex with checks and sees you have the herpes state. They can therefore logically infer that I also have herpes, since you claim you didn't have herpes before and I was the only person you can in contact with in between. They can arrive at this conclusion no matter where in the world I am.

      Quantum teleportation is like me calling you on the phone and giving you herpes that way. There still has to be some contact, but in this case it's phone herpes.

      So while Voyager could still use this technology to communicate, it would still have to make that phone call and wait 17 hours for the light to travel to Earth.

  • Seems like a strange place to do quantum research.
  • Put Another Way (Score:5, Insightful)

    by Anonymous Coward on Thursday September 06, 2012 @09:35AM (#41246935)

    So, it's not teleportation. Thanks.

    • by ceoyoyo ( 59147 )

      It's actually precisely the way teleportation works in Star Trek and most other fiction. The teleported version is a copy that it reassembled at the destination. Usually the original is destroyed (which is actually a requirement of real quantum teleportation), except when the writers are stuck for a plot idea and there's a teleporter accident.

      • by h4rr4r ( 612664 )

        Which means it is not transporting anything. Just murdering and making a copy of the victim.

        Sure the copy thinks he is the one who stepped into the device at the other end, but he is not.

        • by ceoyoyo ( 59147 )

          Yours is a semantic objection, and a nonproductive and ridiculous one at that. If you take a one year round the world trip, the "you" who arrives home won't be the "you" who left either. Essentially all of your atoms will have been swapped for others. Does that mean airplanes, cars and ships aren't transporting anything either?

          • by h4rr4r ( 612664 )

            It is not semantics.
            The person who started the trip and ended the trip using conventional methods was made of all the same stuff and changed slowly over time. Instead of just a exact replica coming out at the end.

            I want to stay alive, not think I stayed alive.

    • It's not teleportation, it's quantum teleportation. Complaining that it's not real teleportation is like complaining that an electron making a quantum leap isn't actually jumping. It's a compound word made up of two smaller words that, when taken together, have a different meaning.

  • Why Satellites? (Score:4, Insightful)

    by sergioag ( 1246996 ) on Thursday September 06, 2012 @09:35AM (#41246945)

    If you are using quantum teleportation, why you even need a satellite???

    • And what does God need with a star ship?
    • Because it's not the kind teleportation you're thinking of. You still need a classical channel.
      • I think his point was valid. If instant communication is possible between a hub in the US and a hub in without wires or line-of-sight issues, there's little point spending the money to put those communication hubs into orbit. Sure we'd still have classical channels leading from those hubs, and we'd still need satellites for things like GPS, but the need for communication satellites would be greatly reduced.

        Of course, the point is moot if the bandwidth sucks on these things. If it's 300 baud, I don't care h

  • I don't understand (Score:2, Insightful)

    by Anonymous Coward

    I don't understand exactly what's going on, so that probably explains why I don't see the advantage of this.
    From reading the abstract I get the impression that they are transmitting the information via lasers to the other location.
    How is this different then using other frequencies in the spectrum? Aren't you still limited to the speed of light? So what is the advantage of this?
    Seems like it adds complication without gaining much, other than being quantum.

    • I agree and I was hoping someone else would have commented by now.

      TFS talks about efficiency. I can only guess that they can improve the bandwidth of the communication by using quantum teleportation but I'm not sure how and would be intrigued to find out.


    • by dingen ( 958134 )

      The main advantage is that it uses a lot less power.

    • As best as I can infer from brushing up from [], what this allows you to do is verify the validity of a message. So I send you a message that says "blah blah blah, and the photon should be in this state", and you check your entangled photon and see that it's in that state exactly so you know you received the message properly from me. It's a reliable signature with superior encryption (since it is provably unforgeable)

      Can someone else correct me or elaborate

  • by gapagos ( 1264716 ) on Thursday September 06, 2012 @09:44AM (#41247057)

    Instead of sending an object (in this case a photon) from one location to another; the information of its quantum state is sent, making a photon on the other end look identical to the original

    With that definition, every time I am faxing a document, I am "teleporting" it. All it does is create a copy of the original object. Can somebody explain to me in which way does this differs as to sending a fax or email and making the fax or email on the other end look identical to the original?

    • by ledow ( 319597 ) on Thursday September 06, 2012 @09:55AM (#41247189) Homepage

      It's not quite as simple as teleportation, it's just given that name: []

      Most specifically:

      "Suppose Alice has a qubit in some arbitrary quantum state

      The components of a maximally entangled two-qubit state are distributed to Alice and Bob.

      In the end, the qubit in Bob's possession will be in the desired state."

      So what Alice is doing is actually modifying the REMOTE qubits to be identical to the LOCAL qubits AFTER the initial information exchange has occurred. You're now literally turning someone's remote blank paper into a copy of the document you have yourself by using a little set of numbers that you determined between yourself last week.

      • You have two cats, one live an one dead. You put them in identical boxes, shuffle them around, and send one random box to someone across the country. When they get the box, they call you up and ask, "what did you send me?" You open your box, and if it's a live cat, you say "I sent you a dead cat," or visa versa.

        No cats were harmed in this description.

    • The quantum state is copied (actually it's not copied, it's transferred - quantum copying would imply faster than light communication)

      Going back to the more common example of momentum plus position, this would be like transferring the momentum and position from one electron to another (i.e. moving one electron into exactly the same place + velocity as the one you are "copying"). There is no measurement of position or momentum happening so the uncertainty principle is not violated and the transfer process ch

    • You destroy the copy on your end leaving the transmitted "copy" as the only one left. At least that's how Star Trek transporters work, sort of.

  • by Anonymous Coward on Thursday September 06, 2012 @09:46AM (#41247087)

    "Quantum teleportation is not how it is made out in Star Trek though. Instead of sending an object (in this case a photon) from one location to another; the information of its quantum state is sent, making a photon on the other end look identical to the original."

    So since matter is energy, if you can make the quantum state of object A identical to object B, IT'S THE REPLICATOR FROM STAR TREK ZOMFG I WANNA CHEESEBURGER

    • mod parent up. while they seem kind of overenthusiastic, it's true that quantum teleportation is a lot more like the replicator in Star Trek than anything else.

  • by SoupIsGood Food ( 1179 ) on Thursday September 06, 2012 @10:08AM (#41247353)

    The reason why we aren't receiving radio signals from distant civilizations is that they're not using radios to communicate... they've figured out something better.

    • by wbr1 ( 2538558 )
      This is a valid assumption. We have only been using radio for an eyeblink in time, and already many of are signals are directed and lower power. Not much noise leakage or signal strength for others to pick up. Assuming technology continues to advance, hat trend should continue, and our radio signal will look more and more like noise at a distance. Then, if better or different technologies supplant radio it's over.
      Who says ET doesn't communicate with lasers, or quantum entanglement, or by manipulating t
  • Can you imagine Xbox 360,000 Live gaming across the solar system.

    Woot! ;-)

  • So basically - you start with two photons next to each, entangle them, then put one on a ship and it sails away. Then, you can tweak the one photon you kept, and every time you do, the other reacts as if you were the one tweaking it? Is it instantaneous? As in, could you put 32 of them side by side and create a 32 bit bus that spans any distance and yet provides connectivity as if where simply plugged into a USB port? Does the reaction on the other end diminish over distance? If not, why not use this to tal

  • The reason for using satellites is that many frequencies of electromagnetic radiation require line-of-sight for communication. Putting a satellite in space gives it line-of-sight to many points one the earth's surface which lack line-of-sight, otherwise I may be wrong, but I was under the impression that quantum teleportation does not have the same requirement of line of sight?

    If it does not require line of sight, doesn't it completely obsolete satellites? Well, I suppose you might use quantum communication

    • by gweihir ( 88907 )

      You are entirely wrong. It is "satellites" because this quantum nonsense cannot deal with intermediate stations! Hence LOS is critical and over these distances you only get it to satellites.

  • And hence, there will not be any "expansion" of it. It is also basically impossible. The Internet is packet-switched. Any quantum-communication method (should it ever be more as a stunt, which is highly doubtful) would necessarily be circuit-switched. ATM demonstrated how bad an idea that is for end-to-end communication.

    Summary: The usual quantum BS. Theory still says it is limited to light-speed (or rather cannot be used for communication at all), the communication is extremely sensitive to any kind of cha

  • by PJ6 ( 1151747 ) on Thursday September 06, 2012 @11:46AM (#41248863)

    It is the hope of the research team that this experiment will lead to commercial use of quantum teleportation to interact with satellites and ground stations. This will increase the efficiency of satellite communication...

    You can't send information via quantum teleportation, so exactly how do they plan to use it in satellite communication?

  • by Datoyminaytah ( 550912 ) on Thursday September 06, 2012 @01:35PM (#41250549)
    OK, here are my questions:

    Assume two entangled particles, two synchronized atomic clocks, and two observers. Each observer has agreed to measure the state of their particle at a predetermined time, relative to their atomic clock. Assume one observer/clock/particle is on a spaceship that has been traveling near the speed of light for some time.

    What happens when the particles are observed? Will the results be the same, because somehow time is "linked" even though it seems to pass differently for each observer? Will the results be different, because the particles are somehow linked "instantaneously?" (What does that even mean in this context?)

    If the former, what happens if the particle is brought back to Earth? We should find the atomic clocks were no longer synchronized. (This part has been tested, right?) If so, wouldn't that mean the particles were permanently out of sync, and that by observing one of them, one could predict the future state of the other? As in, predicting the future?

    IANAP, just pointing out some apparent paradoxes that for all I know have been solved.

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