Quantum teleportation over 143km smashes distance record

Quantum teleportation over 143km smashes distance record

Summary: International researchers say their work paves the way for global quantum communications. Next up: the quantum internet?

TOPICS: Emerging Tech

This month, two major studies on quantum teleportation have made it through peer review and been published, breaking previous distance records. Chinese scientists report teleporting photons over 97km and now a team working in the Canaries report doing the same thing, but between the islands — a distance of over 140km. Both experiments were completed earlier this year and have now been published in Nature.

The researchers from the Austrian Academy of Sciences, and the University of Vienna, say their work paves the way for global quantum communications.

Lead scientist Anton Zeilinger said: "Our experiment shows how mature quantum technologies are today and how useful they can be for practical applications. The next step is satellite-based quantum teleportation, which should enable quantum communication on a global scale."

Quantum teleportation is not a physical process as we would normally understand it. Even calling it 'sending' information is misleading, but language can only do so much.

Quantum entanglement

To understand what is going on, first we need to understand entanglement. This is the property that occurs when two or more quantum bits are linked together in such a way that whatever happens to one of them will produce an immediate change in the other. Often, these pairs are made by splitting a single photon into two, creating an entangled pair.

The idea is that we could use very distant entangled photons to send information over very long distances, securely and instantly, thus building a quantum internet. But making that work is harder than writing it down.

Generally, quantum communication is run through familiar optical fibre. But in this case, the distance was so great that the signal loss would be "too severe", according to the researchers. Instead, the team used lasers to send photons directly through the atmosphere.

Xiao-song Ma, one of the scientists involved in the experiment, said: "The realisation of quantum teleportation over a distance of 143km has been a huge technological challenge."

"An important step for our successful teleportation was a method known as 'active feed-forward', which we have used for the first time in a long-distance experiment. It helped us to double the transfer rate".

This method involves the researchers in sending conventional data alongside the quantum information, which enables the recipient to decipher the transferred signal more efficiently.

Zeilinger adds that his research team is now working with colleagues at the Chinese Academy of Sciences to design and develop a quantum satellite mission.

Topic: Emerging Tech

Lucy Sherriff

About Lucy Sherriff

Lucy Sherriff is a journalist, science geek and general liker of all things techie and clever. In a previous life she put her physics degree to moderately good use by writing about science for that other tech website, The Register. After a bit of a break, it seemed like a good time to start blogging about weird quantum stuff for ZDNet. And so here we are.

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  • This is waaaaay above my pay grade

    This stuff is waaaay above my pay grade, but reading... er skimming... er trying to make a teeny bit of sense out of this WikiPedia article:


    It would seem that at best what you've got here is a method for implementing unbreakable encryption, rather than a process by which one can communicate instantly over vast distances.

    But again, this is waaay above my pay grade, so I could be completely wrong about that.
  • but wait...

    I thought that quantum entanglement did not care about intervening objects. It was supposed to be able to 'instantaneously' affect the partner. This experiment relied on the old fashioned laser based transmission of old school data along with the entangled force. Seems like half a loaf to me.
    • You kind of have to move the entangled bits.

      At least, that would be my informed opinion. Splitting a photon give your two entangled pieces, but to be able to transmit data using entanglement, one of those pieces has to be...well, somewhere else. I'd imagine they're using the laser to send half of the split photon.

      Or I could just be talking out my ass, but that's what I'd guess.
      • Yes, that's right.

        Your ass is smarter than you think. That's exactly correct. Once half of the entangled pair is remotely located, the transmission is instantaneous and cannot be physically blocked.
        • Aerowind has the right idea, omb00900, not so much.

          The common mis-conception is that information is being sent instantaneously. There is no _transmission_ of information that is simultaneous. In fact, the guy who decided to stick "teleportation" on this phenomena really deserves a good kick, since it leads a lot of people to incorrect conclusions. It would be better to call it quantum "decryption."

          Think of it this way: it's more like an encryption key. You each have duplicate keys (the entangled quanta) which can be used to read the information. What quantum entanglement does is allow you to send quantum information (with the highest theoretically possible efficiency) and perfectly "decrypt" it at a remote location, since the two entangled pairs are identical and evolve in an identical way. The fact that the two entangled elements evolve identically is what is simultaneous, not the transfer of information.

          Its like tearing a playing card in half and putting it in two envelopes. I can send those envelopes to people on opposite sides of the world, and have both open their envelopes at the same exact time. The instant one opens his envelope, he now instantly "knows" what is in the other envelope. That information (the number and suit of the card) hasn't traveled between the two of them when one opens the envelope, the information was already there.

          Unfortunately, quantum data is altered (or destroyed) simply by reading it. Imagine an encryption scheme that alters the message data just by trying to decrypt it, whether or not you are successful. If you don't have the right key, you destroy the message. Note that besides enabling a near-infinite encryption key, this makes snooping in on quantum data immediately recognizable without a far more difficult form of a "man in the middle" attack: A thinks he has a quantum entangled pair with B, but C intercepted it and gave half of C's second pair to B.

          Another reason it is useful, in my understanding, is that Quantum data has a tendency to degrade, but though the use of quantum mechanical shenanigans, using a quantum entangled pair to encode-decode the qubits of data allows you to exactly replicate the original quantum state measured at the source when it arrives at the destination.
          • Now for the Sci-Fi: "Real" Teleporters can use this technology

            See, the problem with "teleporting" a human being is that if you want to exactly replicate a person at a distance, down to their exact quantum state, you have to destroy the quantum states in the process of "reading" them.

            (Yes, the process starts by disintegrating you...no wonder Bones was always so nervous.)

            You now have many gajillion bytes of data describing the quantum state of every particle of your body. This information can be transmitted at the speed of light.

            If you have a set of entangled quanta on both ends (transporter pads?) you can now use the transmitted state data to exactly recreate you on the other end, quantum state by quantum state.

            Theoretically possible? Yes. Practical? No.

            I'd rather use a large quantity of negative energy to punch a wormhole in space-time to connect my "here" to your "there." At least I get to stay in one piece.
          • Sounds correct

            And then there is the question you touched on in your first post regarding whether or not the transmission of information and remote reconstitution of matter actually equates to teleportation. And if so, what are the metaphysical implications? I definitely would not want to be the first person to step into one of these machines.
            Alan Barnes
    • I kept laughing...

      about your "half a loaf" figure of speech. But yeah, that's what I thought too.
      Samuel Koh
  • Once the protons are "relocated".....

    Once the entangled proton pair is separated doesn't that mean that other than the act of physically moving the one from the other the first time that all future transmissions will be instantaneous?
    Brayden Tuscher
  • Benefits = instant communication, very SF and is it really possible?

    A communication Earth - Mars could take up to 20 minutes, if the two planets are very far apart. This makes the communication quite inconvenient. By exploiting the property of Quantum entanglement, the communication is instant. Because the pair of entangled photons react instantly, regardless of the distance. Actually they can be each other on the opposite side of the galaxy.

    This represents a huge technical challenge, as how to make sure each party receive exactly the entangled photons. Even if this works, there is a violation of a physical law that I don't know where to spot the flaw: things can travel faster than light, as long as there is no transmission of information. Here there is very meaningful transmission of information.
    • Speed of light

      Well, my understanding (such as it is) is that none of the information is actually "travelling", per se. You're not "moving" data from one photon to the other. The property of quantum entanglement means that whatever happens to one photon automatically and instantaneously happens to the other one. So, you're not breaking the laws of physics by "moving" something faster than the speed of light since nothing is actually "moving" in the physical sense. Or, I could be completely confused and 100% wrong. Most of this is well over my head.
  • Spooky Action at a Distance

    This article does not do justice to the notion of quantum entanglement (perhaps that wasn't the intention), which Einstein called a "spooky action at a distance". You know you're on to something when you've confounded Albert!

    Even gravity does not travel faster than light. If you magically removed the sun from the solar system in an instant, it would take roughly eight minutes before the Earth stopped orbiting and flew off into space.

    The notion of QE confounds physicists and, I believe, holds the secret to much that currently escapes us (unified field theory, dark matter and energy, etc.).
    • We don't THINK gravity

      moves faster than light, but there is still some debate on this matter. According to relativity, gravity is a deformation in space-time, and space-time changes are not limited to the speed of light (see inflationary theory). Supposedly, a quantum theory of gravity (if we can ever actually come up with one that works) will put a speed of light limit on gravity.
      • Dimensional Effects

        Dimensional effects would look 'faster than light' from our perspective. Like the difference between 2 points on a piece of paper lying flat on your desk, versus that distance when you fold the paper in half. The 2 dimensional distance is unchanged, but in 3 dimensional space, folding the paper eliminates the 'actual' distance. So the entanglement is partly an expression of extra-dimensional space. If you believe that sort of thing. :)

        I will be interested to see how this enables us to communicate with deep space probes. This stories reminds me of what it must of been like to hear about Marconi's invention for the first time. Simple concept, hard math. Too hard for me.
  • What does this say about SETI?

    I was always a bit dubious about the whole premise of searching extraterrestrial radio waves for signs of intelligent life. Even before there was active development in quantum communications, I often wondered why people thought that radio wave transmission of the type we've had for barely more than 100 years was going to be something that civilizations would be using for extended periods in their history. As it now stands, it looks like that within 50 years, major communication trunk lines, and links from earth to satellite and planetary probes will be quantum based. Meaning that it would have taken just about 150 years for radio to go from invention to common use, and then to fading obsolescence -- which is basically a blink of the eye in terms of human history at least. Maybe we are looking for the wrong thing with the wrong tools....
    • Yes

      Yeah we are probably looking for the wrong thing with the wrong tools, but they are the only things we know how to look for and the only things we can currently build tools to look for.

      From reading the article, looking for a laser base communications would probably be our best chance of spotting Quantum communications, but until we know QE actually works it will be a long time before we can come up with a detection system.
    • We search for what we understand

      and right now radio and laser are the best shot that we've got. I'm not sure you could actually search for QE as they wouldn't really be a transmission. As I understand it (brain is hurting now) you would need to have one entangled particle at the 'transmitter' and one at the 'receiver'. Change one of them and the other responds instantaneously. But there is no actual transmission between them so there would be nothing to intercept. Of course, a lot of this depends on if you can actually separate the entangled particles that far and whether you can control them enough to make understandable changes to their state. There's plenty of debate about that.
  • What Entanglement Really Means

    I think the original article misinterprets what "quantum entanglement" really means, although this is how it is usually (incorrectly, AFAIK) described.

    Suppose you have two particles which you entangle, and you want to measure their spin. Because they are entangled, if you measure the spin of one of them and it shows "spin up", then if you measure the other one, no matter how far away, it will show "spin down".

    But there is no way for you to FORCE the first particle to have spin up -- all you can do is measure whether the spin it has is up or down. And if you do, and and then try to measure the other particle's spin along a different axis (say left-right, which is perpendicular to up-down) the chance of it being left or right is 50/50. But what if you try to measure along another axis, say at 45 degrees from the first instead of 90? Then the CHANCE of it being one way is somewhat less that 1/2 and being the other way is somewhat more.

    But this is only probability. Remember that spin is quantized. So if the two particles are fermions, meaning they have half-integral spin,, then measuring the spin of either of the particles along ANY axis will give either +1/2 or -1/2. So you can only measure the two particles and be sure that spin is conserved ( +1/2 plus -1/2 = 0) if you can measure them both along the VERY SAME AXIS. If you are off by even a millionth of a degree there is a (admittedly, very small) chance that they will both have the same sign, so spin would appear to not be conserved..
    • Ohhh nowww I understand

      it's all perfectly clear...
      "Just a moment, just a moment"...
      nope, lost it...
      oh wait it's back...
      no, no, argh, gone again
    • Partial understanding

      Though, isn't the spin; (say "spin up" for the first particle).

      Let's say for hypothetical purposes that the first particle is permanently in the "spin up" rotation. Now, if you measure the spin of this particle, would the spin of the entangled second particle always be "spin down"? Or is the spin of the second particle something that cannot be assumed and must be measured?
      (Of course assuming that your measurement was perfect and you measured along the vertical axis of the first particle.)
      Kenneth Astle