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Scientists Race To Establish the First Links of a 'Quantum Internet' 82

Posted by Unknown Lamer
from the violate-causality-for-fun-and-profit dept.
ananyo writes "Two teams of researchers — once rivals, now collaborators — are racing to use the powers of subatomic physics to create a super-secure global communication network. The teams — one led by Jian-Wei Pan at the University of Science and Technology of China, the other by his former PhD supervisor Anton Zeilinger of the University of Vienna — have spent the last 7 years beating each other's distance records for long-distance quantum-teleportation. They now plan to create the first intercontinental quantum-secured network, connecting Asia to Europe by satellite."
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Scientists Race To Establish the First Links of a 'Quantum Internet'

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  • Couldn't quantum teleportation (paralell with some form of classical communication like the internet) be used as an uneavesdroppable communication channel?

    • by Anonymous Coward

      The article goes into details about actually teleporting photons to the satelite... the Summary is Deceptive

    • by slew (2918) on Wednesday December 05, 2012 @03:37PM (#42195057)

      Actually, in a practical system, quantum teleportation would generally be used to exchange an entangled photon from which a key can be extracted, the data would sent later using a classical communication technique (like the internet) using classical symmetric encryption scheme (say, like AES-CBC). Of course if the message is small enough, you might just transport the message entangled (instead of just a way to key the encrypted message), but that's much less efficient using current QM entanglement techniques***.

      Today key exchange is often done with public-private keys, but the mathematical techniques behind them rely on "trap-door" functions (functions that are relatively easy to compute, but much harder to invert). Hard != impossible, so something that is merely hard to invert today, might be easy in the future. With a quantum key exchange scheme you don't transmit the key, only an entangled photon. Thus can't invert it (with currently known physics), and you can't even intercept it (w/o being detected), so it's impossible to deduce the key even in the future. Of course you could always resort to older time-tested techniques like this [xkcd.com]...

      The reason they need the satellite is to transmit the entangled photon (which is used to extract the key). A classical communications channel is effectively a cascade of store-and-forward (every amplifier and digital buffer along the way) so that every stage is making an "observation" and collpasing the quantum state. You basically want to convey the exact same photon you entangled so that the other side can receive it w/o the communication channel observing it in transit. Ideally, you'd bounce a batch of entangled photon off a satellite and the receiver gets the same photons you sent on the other side. Then both sides extract a key from their respective batch of entangled photons and use that key to exchange the message.

      Of course, in a fancier system you might use that one entangled photon to quantum teleport some entangled qubits, but that would be more complicated.

      ***With current QM techniques, you don't really encode a pre-chosen key by somehow "entangling" it into a photon, you are basically creating a type of mind-meld (entanglement) of two photons in a way so that a quantum measurement made on one correlate with the other. With this, magically each side can extract the same information from their respective entangled photons meaning the same bit of information emerges from these measurements. That is why if someone intercepts the photon and retransmit it, both sides would know because they are unlikely have extracted the same bits from the measurments because with currently known physics it's not possible to observe and exactly recreate a quantum state (although apparently you can teleport it). If that doesn't make sense, it's because QM is not supposed to make sense, it just is (or maybe I'm not explaining it very well).

      • by mpeskett (1221084)

        If that doesn't make sense, it's because QM is not supposed to make sense, it just is (or maybe I'm not explaining it very well).

        When we think reality is confusing, that's a fact about us rather than about reality - QM (or whatever the actually true laws of physics turn out to be) got here first, has always been in force, and has created that "normal" looking world we're all so used to. A severely curtailed approximate model was good enough to locate ripe fruit and throw rocks at each other, so that's what we find intuitive, but we're the weird ones - imagining the universe operating on the basis of tiny little billiard balls bopping

    • by tehcyder (746570)

      Couldn't quantum teleportation (paralell with some form of classical communication like the internet) be used as an uneavesdroppable communication channel?

      Yes. Or no.

      I'm quite the quantum guru today.

  • evesdropping (Score:5, Insightful)

    by schneidafunk (795759) on Wednesday December 05, 2012 @02:47PM (#42194477)
    Does evesdropping on a quantum message destroy the message? People talk about super secure quantum messages because it leaves a detectable trace, but does it also destroy the message in the process?
    • Re:evesdropping (Score:5, Informative)

      by JesseMcDonald (536341) on Wednesday December 05, 2012 @03:00PM (#42194647) Homepage

      Does evesdropping on a quantum message destroy the message?

      Not exactly. The eavesdropping is actually detected during the key exchange (the "quantum" part), so if eavesdropping is detected, the message is never sent in the first place. If the key is exchanged without any eavesdropping, the message is encrypted with a one-time pad and sent through more traditional channels.

      One-time pads are not vulnerable to cryptoanalysis—not even brute-force searches, as there is a valid key for every possible message (up to the observed message size), and no way to tell which one is the right one. The problem with one-time pads has always been key exchange, since you need a new, never-before-used bit of shared key for every bit of message. Quantum mechanics provides a way to generate shared keys for one-time pads without the risk of anyone eavesdropping (undetectably) on the key exchange.

      • Re:evesdropping (Score:4, Informative)

        by The Raven (30575) on Wednesday December 05, 2012 @04:40PM (#42195691) Homepage

        This is not quite true. True one-time pads are not able to be brute forced, but the pad must be as long as the message (10MB file = 10MB key). This is not how quantum key exchange is expected to work. The quantum key will be measured in KB, to encrypt a secure session or file measured in MB or GB. This means that it is damn secure, but could be brute forced given enough time.

        The bit rate on these quantum links is not high enough for it to be practical to exchange pads the size of the file.

        • I always thought that using a one time pad could use something like a simplified key. Take a irrational number like Pi, and then use an offset and size (length) for the pad instead of the whole key.

          Pi offset 5,340,590,934,232,301 Length 2^19

          Of course, it may be just that kind of setup is just as easy to crack as double ROT 13.

          • I always thought that using a one time pad could use something like a simplified key. Take a irrational number like Pi, and then use an offset and size (length) for the pad instead of the whole key.

            The critical part of a one-time pad is that each bit of the key is truly random: there is one bit of entropy for each bit in the key. Anything less amounts to reusing bits from the key, so it's no longer "one-time". What you've described is essentially a form of pseudo-random number generator, with the offset into Pi as the seed. A PRNG can form the core of a symmetric encryption algorithm—just XOR the pseudo-random bit-stream with the message—but it isn't a one-time pad because the entropy of t

        • Quantum cryptography in the popular "provably unbreakable by physical law" sense is indeed a one-time pad, and requires the secure distribution of a random key bit for every bit of the message. As you pointed out, however, the bit-rate of QKD is limited, at least for now. If you need to send a lot of data, and you're willing to settle for an algorithm subject to brute-force searches and other forms of cryptoanalysis, possibly including quantum algorithms, you can use QKD to derive an (arbitrarily large) sha

      • Not exactly. The eavesdropping is actually detected during the key exchange (the "quantum" part), so if eavesdropping is detected, the message is never sent in the first place. If the key is exchanged without any eavesdropping, the message is encrypted with a one-time pad and sent through more traditional channels.

        The details of the key exchange part is what is most interesting.. it can't be a fully quantum process since there is no possibility of binding identity to the quantum channel.

        Verification of identity requires classical communication and standard encryption technology to verify an OTP peer.

        An attacker pretending to be copious noise can still probe your initial key. If the key is later compromised an attacker could leverage the verifier during key exchange to obtain clues about subsequent OTP data transmitt

        • You raise a good point. QKD ensures that you share the key with exactly one peer; it doesn't say anything about who that peer is. If, rather than simply eavesdropping, someone managed to redirect the channel to their own equipment, you could end up sharing the key with the attacker rather than the intended recipient.

          For this reason, all QKD protocols require an authentic (but public) classical communication channel in addition to the eavesdropping-evident quantum channel. Once the peer has been authenticate

  • by Anonymous Coward

    Now the rest of the world can proceed to steal their technology and not pay them for it.

  • Yay! QE is a major component of my scifi book's communications. Yes, it's a crappy book, but it is my crappy book... and you can read it online without DRM, blah blah blah.

    http://cruft-private-janitorial.com/?chapter=1 [cruft-priv...torial.com]

    Can't wait for animated breakfast bar wrappers! Or Capt. Skyking brand Starling!

    • My thought was timed reading... where you only read the next qubit at predefined intervals to check for state.. and what is definitely a gross misunderstanding of QE (but useful as narrativium) - writing a state to the next particle. so particles are read-write in order, and they slowly "tick away"... but the base set are linked into the network.. so you can buy any random batch of particles and they link back to some other endpoint.

    • by mcgrew (92797) *

      Why not post it as a series of slashdot journal entries? [slashdot.org] Probably not a lot of slashdotters who don't like science fiction!

  • I promise you they will have it working in a week.

  • I'll help (Score:5, Funny)

    by AuMatar (183847) on Wednesday December 05, 2012 @03:42PM (#42195087)

    I can start making Schrodinger's Lolcats. Until you open the link, you don't know if its funny or not.

    • by harrkev (623093)

      In the jpegs, the girl will be simultaneously clothed and nude at the same time.

      • by drkim (1559875) on Wednesday December 05, 2012 @04:03PM (#42195289)

        In the jpegs, the girl will be simultaneously clothed and nude at the same time.

        Yes. But the big problem with quantum porn is that it's hot and nasty; until you actually look at it, then they are always fully clothed and sitting around talking about how men objectify them.

  • There is zero need, zero benefit and zero possibility of actually creating more than small demonstration.

    • by CodeHxr (2471822)
      There's also no need for anyone to have more than 640k of RAM, right?
  • Now we can be at war with Eastasia and allied to Eastasia at the same time!
  • Don't know the capacity of present day photon traps, but if they could squeeze in say a couple of petabytes of those quantum entangled photons simultaneously into two photon traps at location A, then FedEx one photon trap to location B, then as I understand it, you would enjoy 1 GBit/s instantaneous IPv4/IPv6 between location A and B (regardless of distance) for say one year. I.E. digging that new Atlantic cable might not be the only option for achieving even higher speed stock trading...
  • How susceptible to DoS attack is this set up anyways ? Real talk.
  • The Tortoise and the Hare.... So which side of entanglement will get there first?

  • So...they're hoping to make a 'Quantum Leap' http://instantrimshot.com/ [instantrimshot.com]

We don't know one millionth of one percent about anything.

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