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Encryption Science

Theoretical Breakthrough For Quantum Cryptography 116

Posted by Soulskill
from the add-qutrits-to-your-super-scrabble-words dept.
KentuckyFC writes "Quantum cryptography uses the quantum properties of photons to guarantee perfect secrecy. But one of its lesser known limitations is that it only works if Alice and Bob are perfectly aligned so that they can carry out well-defined polarization measurements on the photons as they arrive. Physicists say that Alice and Bob must share the same reference frame. That's OK if Alice and Bob are in their own ground-based labs, but it's a problem in many other applications, such as ground-to-satellite communications or even in chip-to-chip communications, because it's hard to keep chips still over distances of the order of the wavelength of light. Now a group of UK physicists have developed a way of doing quantum cryptography without sharing a reference frame. The trick is to use entangled triplets of photons, so-called qutrits, rather than entangled pairs. This solves the problem by embedding it in an extra abstract dimension, which is independent of space. So, as long as both Alice and Bob know the way in which all these abstract dimensions are related, the third provides a reference against which measurements of the other two can be made. That allows Alice and Bob to make any measurements they need without having to agree ahead of time on a frame of reference. That could be an important advance enabling the widespread use of quantum cryptography."
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Theoretical Breakthrough For Quantum Cryptography

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  • by Anonymous Coward on Monday March 08, 2010 @10:27AM (#31400948)

    One thing, with quantum crypto, the code changes when you look at it. In other words, you have to know the key before seeing it.

    Two, it kills a LOT of cats! You get the code right, and BAM! dead cat.

    PETA will be against this!

    • Yeah, that's just what I was going to say. He stole my idea!

      You just have to wrap the secret bit-thingies in double-secret bit-thingies and before you know it's you're a tenured professor because nobody knows what the hell you're actually doing.

      Just wait until he replaces the dilithium crystals with Folgers, then we'll really be in trouble.
    • by Chris Burke (6130)

      Two, it kills a LOT of cats! You get the code right, and BAM! dead cat.

      I always suspected that all this "entangling photon pairs" and "quantum encryption channel" stuff was just a bunch of scientists jerking off, but I didn't think they were actually euphemisms for spanking it!

      • I always suspected that all this "entangling photon pairs" and "quantum encryption channel" stuff was just a bunch of scientists jerking off...

        Exactly. This is sort of why I am deeply suspicious of quantum cryptography. When is a cat not a cat? Look at your data sideways, and it suddenly realises that it's not supposed to exist?

        Oh wait, that sounds like a Microsoft filesystem... ;-)
    • by AmigaMMC (1103025)
      It's ok, cats taste good. I hope they're not too entangled though or they get between my teeth.
    • Accidentally modded you troll. My bad. Posting to undo.
  • qutrits? (Score:1, Offtopic)

    by Nadaka (224565)

    Applying the standard naming conventions would result in qutits. I much prefer qutits.

    • Re: (Score:3, Interesting)

      by Nadaka (224565)

      Especially when dealing with entangled triplets.

    • Re: (Score:3, Funny)

      by ArsonSmith (13997)

      cute tits or quit its?

    • Re: (Score:1, Troll)

      Applying the standard naming conventions would result in qutits. I much prefer qutits.

      And the scientific community would be rather better off choosing names that let us focus on the furtherance of humanity's knowledge of the inner workings of the universe than opening the door for juvenile jokes.

      • Re: (Score:1, Funny)

        by Anonymous Coward

        Applying the standard naming conventions would result in qutits. I much prefer qutits.

        And the scientific community would be rather better off choosing names that let us focus on the furtherance of humanity's knowledge of the inner workings of the universe than opening the door for juvenile jokes.

        The planet Uranus thanks you.

        Everyone else thinks you're a bit too uptight.

      • Re: (Score:1, Offtopic)

        by Nadaka (224565)

        Hint...

        This was in fact a juvenile joke.

        I wasn't being serious.

        Do I need to use smileys or [/joke] ubbcodes in every post?

        • by mwvdlee (775178)

          Do I need to use smileys or [/joke] ubbcodes in every post?

          Yes. You do. In every post.

    • As Howard Tayler of Schlock Mercenary notes,

      the same abbreviational logic that turned "binary digit" into "bit" turned "trinary digit" into "tit." This nomenclatural error set computing back nearly three hundred years, and two entire generations of promising computer scientists were lost trying to keep abreast of bad puns.

  • Someone please correct me if I'm wrong here, and I haven't had time to read the entire article, but wouldn't this also bypass the conventional data transmission necessity for quantum communications?
    • Re: (Score:2, Interesting)

      by Threni (635302)

      Would this system still allow alice/bob to know if someone's evesdropped? What's the difference between a hostile evesdropper and just some other part of the infrastructure for getting data from alice to bob? Without that, quantum cryptography is just another encryption system, and there are nothing wrong with the current ones. Right? (It would arouse me if replies to this post started simply "Wrong.")

      • Re: (Score:3, Funny)

        (It would arouse me if replies to this post started simply "Wrong.")

        Not to judge your lifestyle choices, but I'm pretty sure that the reason no one has replied as such has to do with the collective will of the community not to see you aroused.

  • Engineering (Score:3, Interesting)

    by SEWilco (27983) on Monday March 08, 2010 @10:38AM (#31401076) Journal
    I think this is engineering, not theory. Theory was the original idea of using entanglement for cryptography. Now they're applying the technology to make it practical, and that's engineering. They're adding a bit of steel or another entanglement to make it more usable. If nobody has built this device yet, it's theoretical engineering.
    • Re:Engineering (Score:4, Insightful)

      by Sir_Lewk (967686) <sirlewk@NospAm.gmail.com> on Monday March 08, 2010 @10:44AM (#31401138)

      What makes you think that theory and engineering are mutually exclusive, with a fine dividing line?

    • Re:Engineering (Score:4, Insightful)

      by Chris Burke (6130) on Monday March 08, 2010 @11:00AM (#31401318) Homepage

      Theory is coming up with a hypothetical mechanism for incorporating extra information so that it doesn't require a known reference frame.

      Engineering is making a device that actually does it reliably.

      As my sibling post said, there's no clear dividing line. But this is definitely on the theory-ish side of it.

      • by idontgno (624372)
        The Billard Ball [wikipedia.org] is the difference between theory and engineering. The Theoretician tells the Engineer it can't be done. The Engineer does it anyway. And the Theoretician "accidentally" kills the Engineer with the resulting invention.
    • Now they're applying the technology to make it practical, and that's engineering.

      After that, the time for the third phase - marketing and selling - will come, when patents, stupid business plans and inflated prices will make it impractical again.

      • by gtall (79522)

        You've discovered the Quantum Theory of Engineering: If it practical enough to produce, Business School Product will screw it up into being impractical to produce. The tricky part is that if Business School Product is practical enough to produce, then Business School Product becomes impractical to produce. When this happens, a fixed point is reached and all the world's business schools go out of business because it is then recognized no one in their right mind would go into the business of building a busine

    • No, in all your years of /. have you never followed one of those developer != engineer rants? For this to be considered engineering, at the very least the failure of the process should put people in mortal danger. Since People != Cats, we can assume this is not engineering. This is priobably more akin to some sort of quantom crafting than engineering.
    • Here's a link to the paper: arXiv:1003.1050v1 [arxiv.org]. Have a read and make a more informed opinion about what field it belongs it.

    • They're adding a bit of steel or another entanglement to make it more usable.

      Didn't IBM do that already in the 90's?

  • by PPalmgren (1009823) on Monday March 08, 2010 @10:41AM (#31401118)

    Boy am I glad I didn't pursue that physics major. The only thing I got out of that is that Alice and Bob needed a marriage counselor to reconcile their differences.

    Anyone mind converting that attempt in layman's terms to something useful, like a car analogy?

    • Quantum physics does not have a car analogy. Cars cant be mixed up and then split so each part has a bit of the other, and not just physically. if one car starts, it means its parts in both entangled sets start and the moment you go and look witch of the cars you have it becomes one or another, instantly causing the other entangled car thingy to become the car you didn't get. Also, fu Eve.
      • Re: (Score:3, Informative)

        by Culture20 (968837)

        Quantum physics does not have a car analogy. Cars cant be mixed up and then split so each part has a bit of the other, and not just physically. if one car starts, it means its parts in both entangled sets start and the moment you go and look witch of the cars you have it becomes one or another, instantly causing the other entangled car thingy to become the car you didn't get. Also, fu Eve.

        Hungarian Physicists and Automotive Engineers are closer to tackling that problem:
        http://tech.slashdot.org/story/10/02/24/1614245/Hungarian-Electric-Car-Splits-Into-Two-Smaller-Cars [slashdot.org]

    • by mrsurb (1484303) on Monday March 08, 2010 @10:53AM (#31401230)

      I'll give it a shot.

      Alice wants to get out of her car and into Bob's car. In laboratory conditions both cars are perfectly still so it's easy. Out on the freeway travelling at high speeds it's a recipe for disaster.

      But these clever engineers have come up with a wonderful design for a semi-trailer that both cars can sit on while being driven down the freeway. Now Alice and get out of her car and into Bob's car for that secret rendezvous. In the middle of the freeway.

      • by JaneTheIgnorantSlut (1265300) on Monday March 08, 2010 @11:15AM (#31401476)
        Do Carol and Ted know about this?
      • by Schiphol (1168667)
        That's not new. The Foundation for Law and Goverment [wikipedia.org] had such a system in place almost thirty years ago. We've seen rehashed stories in /. before, but really, guys, 30 years?
        • by HTH NE1 (675604)

          Well, you have to consider that FLAG wasn't confident enough about the capabilities of their car's artificially intelligent on-board computers to recognize its driver to not require a hidden fingerprint scanner underneath its door handles as an access control.

        • That's not new. The Foundation for Law and Goverment [wikipedia.org] had such a system in place almost thirty years ago. We've seen rehashed stories in /. before, but really, guys, 30 years?

          That was Bonnie and Michael (yeah, we saw those furtive glances). This article is about Alice and Bob. Try to keep up.

      • by slayer_ix (927649)
        Nice analogy *internet high five*
      • by jbezorg (1263978)

        But these clever engineers have come up with a wonderful design for a semi-trailer that both cars can sit on while being driven down the freeway. Now Alice and get out of her car and into Bob's car for that secret rendezvous. In the middle of the freeway.

        Eve hijacks the semi-trailer... shocking film at eleven.

      • by ascari (1400977)
        What's wrong with just parking?
      • I use the Earth for similar purposes.

        Nobody seems to care about my "I do it at 365km/s relative to the Virgo Supercluster" bumper sticker though.

    • Re: (Score:3, Informative)

      by Tyler Durden (136036)

      Here's my own amateur shot at it. If I'm wrong, I'm sure someone who knows better will correct me. Oh, and fuck the car analogy.

      The quantum entanglement measurements will only work with two entangled photons when the velocities and accelerations of the two parties involved are the same. But if you're doing it with two objects with different motion, say a person on the ground and a satellite orbiting the earth, it won't. The satellite is in free fall and, according to general relativity, not in an accele

      • Re: (Score:3, Informative)

        by HTH NE1 (675604)

        The satellite is in free fall and, according to general relativity, not in an accelerated reference frame.

        If you're not moving in a straight line at a constant speed, you're in an accelerated reference frame. Satellites are in orbit; there's no such thing as a straight-line orbit.

        • Are you sure about that? It was my understanding that since it's free-falling in orbit that according to general relativity it was going in a straight line through space-time.

        • there's no such thing as a straight-line orbit.
          Find an orbit where you pass through one of the Lagrange points. While you are in the Lagrange points, you are moving in a straight line, because all accelerations cancel each other out there.

          • there's no such thing as a straight-line orbit.

            Find an orbit where you pass through one of the Lagrange points. While you are in the Lagrange points, you are moving in a straight line, because all accelerations cancel each other out there.

    • Re: (Score:1, Interesting)

      by Anonymous Coward

      No car analogy, but I think I summarize it a little simpler (though I am no expert).
      In Quantum Cryptography it's possible to detect the presence of an eavesdropper. The eavesdropper, by the act of listening changes the transmission of the signal and is provably unable to put it right again. This is possible because of some physics mumbo-jumbo and is highly sensitive to the distances between the people involved.
      As best I can make out, this research used more physics mumbo-jumbo to encode the distances betw

  • by Conspiracy_Of_Doves (236787) on Monday March 08, 2010 @10:51AM (#31401208)

    "This solves the problem by embedding it in an extra abstract dimension, which is independent of space."

    Has it occurred to anyone else how UNBELIEVABLY FRIGGIN' COOL it is that a line like that shows up in an article that is talking about building an actual, physical device?

  • by genghisjahn (1344927) on Monday March 08, 2010 @10:55AM (#31401256) Homepage
    Glap glar photons biddle doo-vack triple photon vajmu double photon zirreyzoo-zah picture frame powlat pweegoo paparazzi photos of Alice and Bob.
  • Dangit... (Score:1, Offtopic)

    by barfy (256323)

    I was all set to sell crypto supplies and repair services in the alternate dimension. Do you have any idea what this is going to do to housing prices there?

  • by fractalspace (1241106) on Monday March 08, 2010 @11:18AM (#31401522)
    Why cant they simply open a sub space channel and use a Tachyon pulse to synchronize the two frames ?
  • I, for one welcome our new quantum overlords.

  • by grepya (67436)

    ... if Alice and Bob are perfectly aligned so that they can carry out well-defined polarization measurements ....

    Oh... so that's what the kids are calling it these days... ??

  • Maybe I'm not up on my vocab as of late, but since when does the phrase "Theoretical Breakthrough" make any kind of sense?
  • I just KNEW there was a third guy involved in there. Bob was never going to satisfy Alice all by himself, all these years.

  • So, this works for Alice and Bob. What about Homer and Jethro?
  • Polarization has a nasty habit of rotating when it travels through optical (telecom) fiber. To make matters worse, the degree of rotation depends on temperature and physical strain and can change quite rapidly. Of course, entangling three photons is much harder than entangling two.

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