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Supercomputing Math Science

Light-based Quantum Circuit Does Basic Maths 198

Posted by Zonk
from the small-steps-start-small dept.
Stochastism writes "In yet another small step toward realistic quantum computing Australian researchers have developed a light based 4-qubit quantum computer. It has already calculated the prime roots of fifteen, three and five. 'The quantum circuit pioneered by the Queensland researchers involves using a laser to send "entangled" photons through a linear optical circuit ... The Queensland research group acknowledged that the theorised code cracking ability of quantum computers may be why Australian quantum computer research is in part funded by a US government defence intelligence agency, the Defense Advanced Research Projects Agency (DARPA).'"
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Light-based Quantum Circuit Does Basic Maths

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  • by InvisblePinkUnicorn (1126837) on Friday December 14, 2007 @04:24PM (#21702526)
    Seven! It does seven maths!
    • Re: (Score:2, Insightful)

      Ever hear of "two countries divided by a common language"?

      one quick reference here [suite101.com]
      There are various accepted abbreviations for the word mathematics, and one is as good as any other. In Germany, the abbreviation is "Mathe," in Britain and Canada, it is "maths," and in the USA, it is "math."

      /tsg/

      • by Chris Burke (6130)
        Ever hear of "two countries divided by a common language"?

        "who then proceed to poke fun of each other over any minor difference"?

        Yes, I've heard of it.
  • But... (Score:5, Funny)

    by SiriusStarr (1196697) <.SumStultusSedEsQuoque. .at. .gmail.com.> on Friday December 14, 2007 @04:24PM (#21702538)
    More importantly, can it run Crysis?
  • In yet another small step toward realistic quantum computing Australian researchers have developed a light based 4-qubit quantum computer.

    4 qubits? How much is that in furlongs?

    hectares?
  • Moore's law (Score:3, Funny)

    by pwnies (1034518) * <j@jjcm.org> on Friday December 14, 2007 @04:35PM (#21702682) Homepage Journal
    I wonder if Moore's law will apply to the number of qubits within a quantum computer as well. A 1024 qubit computer within the next 20 years would be nice.
    • by moderatorrater (1095745) on Friday December 14, 2007 @04:56PM (#21702948)
      Nobody would ever be able to use 1024 qubits.

      -moderatorrater, 2007
      • Re: (Score:2, Funny)

        by GeekZilla (398185)
        "Four Qubits should be enough for anyone."
      • by Nazlfrag (1035012)
        Just wait till the RIAA finds out you've been representing every single sample they ever made simultaneously. I'm pretty sure a fine of $150,000 * (2 ^ 1024) would be seen as fair and reasonable compensation by an impartial court.
    • Re: (Score:3, Informative)

      Probably not. Moore's law is a very specific and narrow-focused trend regarding the number of transistors that can be placed on a chip to achieve the highest cost effectiveness. Any major shift in technology (i.e. away from traditional transistors) will have it's own completely different trend. There's no inherent trait in computing as a whole that gives rise to Moore's law.
      • by gd2shoe (747932)
        There have been a number of similar patterns within computing. Memory and Hard disk densities come to mind. While memory density may also be linked to transistors, hdd density is not.

        I think the question was valid. While it wont be "Moore's Law" technically, it may well follow a predictable exponential trend.
        • Well if your only requirement for somethings to be "Moore's Law"-ey is that it follows an exponential curve, then there are thousands of things that follow Moore's Law. Just as there are plenty of things, even computer related, that do not follow, such as memory latency.

          I guess I just have a general aversion to using the terminology of Moore's Law instead of just saying exponential growth. Moore's Law is a very specific observation on the cost effectiveness of transistor count per chip (not density spec
    • The Xbox public key was 2048 bits. I'd love to see the end of that once and for all, now that the console is dead. I don't think it'll be possible any time soon, if at all.

      I wonder about quantum computing - it could turn out to be the case that fighting decoherence requires energy exponential in the number of qubits. This would mean quantum computing is worthless. It would also be another instance of nature conspiring against those who attempt to break its laws.
  • Err (Score:3, Interesting)

    by zsouthboy (1136757) on Friday December 14, 2007 @04:39PM (#21702724)
    I was under the impression that we couldn't simply use PHOTONS as qubits - because while photons do have a quantum state, they get all...destroyed.

    Of course, the article doesn't help.

    Anyone?
    • Re:Err (Score:5, Informative)

      by SeekerDarksteel (896422) on Friday December 14, 2007 @05:01PM (#21703016)
      You can use ANY quantum mechanical system with two discrete states as a qubit, just as you can use any classical mechanical/electric system with two discrete states as a bit.

      Typically with photons, it consists of the direction of polarization of the electro-magnetic field associated with the photon. Straight up and down represents one state, horizontal represents the the second state, and the photon can be in a superposition of both of these states.

      Saying that photons get "destroyed" is irrelevant so long as we can measure the photon's polarization when it gets destroyed because as soon as we measure the polarization, the quantum state of the photon is destroyed anyway and becomes worthless to us. This is true of any quantum mechanical system, so whether the system representing the qubit sticks around or disappears after being measured (whether a photon, electron spin, or otherwise), is only a matter of logistics of the quantum computer, not of the actual computation.
  • Huh? (Score:4, Funny)

    by RecoveredMarketroid (569802) on Friday December 14, 2007 @04:41PM (#21702754)

    It has already calculated the prime roots of fifteen, three and five.
    Prime roots of three and five? Boy, the quantum world is weird!...

    Parse error! Parse error!
    • by swillden (191260)

      It has already calculated the prime roots of fifteen, three and five.
      Prime roots of three and five? Boy, the quantum world is weird!...

      And fifteen, too. The roots of fifteen, three and five are all irrational, and since primes are integral and therefore rational, none of them can be prime.

    • Re: (Score:3, Funny)

      by Fx.Dr (915071)
      "Ask it to divide by zero or the cat gets it!"

      The cat was both shot, and not. It was half a tragedy. We all cried furiously, and didn't.
    • by Alsee (515537)
      calculated the prime roots of fifteen, three and five.
      Parse error!


      I think they mean factor, not root. That makes the parse error go away.

      Based on that assumption, I tried the calculations myself. I've been able to solve the last two (one answer is {3} and the other is {5}), but that first one is a real bitch to solve. I think the answer might involve more than one number.

      -
  • Me too! (Score:5, Funny)

    by Daffy Duck (17350) on Friday December 14, 2007 @04:46PM (#21702812) Homepage

    It has already calculated the prime roots of fifteen, three and five.

    I, too, have already calculated the prime roots of fifteen, with nearly identical results. Where's my DARPA funding?

  • by bubbl07 (777082) on Friday December 14, 2007 @04:53PM (#21702910) Homepage

    It has already calculated the prime roots of fifteen, three and five.
    -1 Redundant.
    • by Nazlfrag (1035012)
      Prime factors:
      15 = 5, 3
      5 = 5
      3 = 3

      Not at all redundant, in fact it is very space efficient!
  • by GeekZilla (398185) on Friday December 14, 2007 @05:02PM (#21703024)
    Q: What kind of room is it kept it?
    A: A Qubicle

    Q: How big is it?
    A: About four Qubit meters.

    Q: Qubit? Wasn't that an early arcade game with a little guy jumping around changing the quantum state of a bunch of Qubes?

    I have OBVIOUSLY had too much Qaffeine.
  • by hyades1 (1149581) <hyades1@hotmail.com> on Friday December 14, 2007 @05:15PM (#21703200)
    Computerized Australian Technology...until you take a good look at it.
  • by p3d0 (42270) on Friday December 14, 2007 @05:16PM (#21703210)
    I once new a guy who could compute the prime roots of 15 in his head.
  • Soon we will be able to test 2^N possibilities in 2N time, but my question is where does that information come from? There's a lot of hand-wavyness on how that actually happens...

    One possibility is that we ask the 'computer' of the universe to do too much computation and end up in an infinite loop, crashed universe, 'dark' part of a mandlebrot-like fractal, etc.

    Another possibility is that the 'computer' of the universe will simply abort operations that take 'too long', the quality of our simulation will de
    • Re: (Score:3, Interesting)

      by jrcamp (150032)

      One possibility is that we ask the 'computer' of the universe to do too much computation and end up in an infinite loop, crashed universe, 'dark' part of a mandlebrot-like fractal, etc.

      I think that the fact that we are here, almost 14 billion years after the universe began, is a good indication that it's not possible to "crash" the universe.

      The original numbers plugged in the Drake Equation estimated 10 intelligent civilizations in our own galaxy. Since there are more than 100 billion galaxies, that me

      • by jamesh (87723)
        Well... it could be that the 'crash' or 'reboot' propagates at the speed of light. So some part of the universe has already crashed and the crash just hasn't reached us yet.

        That being said, it's a fairly safe bet that anything to do with physics probably happens inside a supernova (every possible particle created, however fleetingly), so if a few supernovae haven't triggered the destruction of the universe I think we're pretty safe.
        • by Alsee (515537)
          it's a fairly safe bet that anything to do with physics probably happens inside a supernova

          I wish we were in a bar. I'd take you up on that bet and snag me a free drink :)
          Easy counter-example, you're not going to find a Bose-Einstein Condensate cropping up in a nova.

          -
          • by jamesh (87723)

            I wish we were in a bar. I'd take you up on that bet and snag me a free drink :)
            Easy counter-example, you're not going to find a Bose-Einstein Condensate cropping up in a nova.

            I did think of the really cold things that probably wouldn't happen inside a supernova (although... you never know :), but the type of action under consideration (eg universe crashing) is probably more likely to happen because of a really 'hot' action than a really 'cold' one.

            This argument would probably attract a lot of really strang

      • > I think that the fact that we are here, almost 14 billion years after the universe began, is a good
        > indication that it's not possible to "crash" the universe.

        How do you know that the universe hasn't crashed and been restored from a snapshot backup? You'd have no means to know, being part of it.

        Anyway since scientists studying the big bang have not discovered any sign of windows startup sequence, an uptime of 14 billion years is feasible.
    • by fredrikj (629833) on Friday December 14, 2007 @05:54PM (#21703630) Homepage
      Soon we will be able to test 2^N possibilities in 2N time, but my question is where does that information come from? There's a lot of hand-wavyness on how that actually happens...

      Phenomena like superposition and entanglement are not fully understood from the metaphysical point of view, and there is some hand-waving about that. But the mathematics agrees perfectly with experiment, and that's all we need to know to put the theory to use.

      One possibility is that we ask the 'computer' of the universe to do too much computation and end up in an infinite loop, crashed universe, 'dark' part of a mandlebrot-like fractal, etc.

      Another possibility is that the 'computer' of the universe will simply abort operations that take 'too long', the quality of our simulation will degrade, and our complex quantum math will result in randomish results.


      How do we know building a quantum computer won't break the universe? Well, the things that go on in a quantum computer are the same things that go on in ordinary matter all the time. A speck of dust consists of some 10^20 particles that continually interact with each other according to the same quantum-mechanical laws that govern the interaction of qubits used in integer factorization. Why should the universe care what purpose we use those interactions for?

      And in the end, a size/time-N quantum computation can be simulated with 2^N space and in 2^N time on a classical computer (I might be wrong about the exact form of those expressions). Would the universe collapse if we run a quantum algorithm on a PC?

      And then there is the possibility held by quantum researchers that somehow the universe can magically perform any amount of complex computation with no cost at all.

      This isn't true. Quantum algorithms have real costs that grow with the size of the problem, just like on ordinary computers. (Concretely speaking, we can simulate them on classical computers in deterministic time.)
    • by 2short (466733)
      "'dark' part of a mandlebrot-like fractal"

      You mean, the part the programmer chose to display as black?

      Fractals aren't magic. Quantum mechanics isn't magic. The fact that you don't understand them doesn't make them magic or mean they might threaten the structure of the universe.
  • by hyades1 (1149581) <hyades1@hotmail.com> on Friday December 14, 2007 @05:18PM (#21703226)
    Computerized Australian Technology lives.....until you take a good look at it.
  • DARPA (Score:3, Insightful)

    by CompMD (522020) on Friday December 14, 2007 @05:18PM (#21703234)
    is not an intelligence agency.
    • by Nazlfrag (1035012)
      Good point, neither is the CSIRO. Still, the logical and most probably intended application of a successful multiple qubit computer is in the intelligence arena, so I can see how the error was made.
  • "One qubit can be in two possible states, two qubits can be in four, three qubits in eight, and so on," explained Professor Andrew White from the University of Queensland, who works on the project. Thus in a quantum computer every additional quantum bit will double computing power.

    I might be missing something but isnt the same just true for regular bits? You know: 1 bit, 2 states; n bits, 2^n states... Are the Aussies playing a joke on DARPA... and still getting funding ? That would be neat...

    • What they're referring to is quantum entanglement. There's a vast difference between having two independent qubits each in a superposition of two states and having two entangled qubits together in a superposition of four states. It's a subtle, but very important difference.
  • by E++99 (880734) on Friday December 14, 2007 @08:45PM (#21704794) Homepage

    It has already calculated the prime roots of fifteen, three and five.

    CRAP! 15 was my RSA public key!
    • by jamesh (87723)

      CRAP! 15 was my RSA public key!

      Bah. That'll teach you. They've been warning you for years about the perils of 4 bit encryption!

      And don't just go and move to 5 bit encryption, i'm sure that that'll be broken any year now. I'd suggest starting at 8 bit, with a plan to move to 16 bit in 18 months or so.

      btw, if this technology has a doubling time trend like Moore's law, does that mean they'll double the number of bits every x months, or add a new bit every x months? I need to know so I can plan my move to 32 bi

    • by Alsee (515537)
      I use a really really long RSA key so I don't have to worry about anyone ever factoring it.
      It's a really cool key too, the last digit is zero.

      -
    • Re: (Score:2, Funny)

      by MattskEE (925706)
      I use the same combination on my luggage!
  • s/prime roots/prime factors/, please. Sheesh.
  • by wickerprints (1094741) on Friday December 14, 2007 @09:37PM (#21705156)
    The article mentions things called "prime roots." This is not a standard mathematical term. Rather, considering the context, quantum computing, and its most discussed potential application--quantum cryptography--it is likely that what was actually computed were primitive roots.

    For the sake of completeness, a primitive root of a prime p is an integer r such that the smallest positive value of k such that p divides r^k - 1 is k = p-1. For large primes, finding primitive roots is not a trivial task. For example, r = 2 is a primitive root of p = 5, since the positive integer powers of 2 are 2, 4, 8, 16, 32, ..., and modulo 5, this becomes 2, 4, 3, 1, 2, .... The first occurrence of 1 is for 2^4, hence k = 4 = 5-1.
  • The big deal about quantum computers (to me anyways) is that supposedly they can break encryption. That's a bad thing obviously. I'm always confused that when we see these stories about quantum computers that nobody is discussing how much longer it will be before big brother can read all my email even when Im wearing my tinfoil hat!

    So what's up with that? I must have some assumptions wrong or the usual sorts would be predicting the sky is falling.

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