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Hardware Science Technology

A "Photon Machine Gun" For Quantum Computers 143

Posted by kdawson
from the entangle-this dept.
An anonymous reader writes "Generating entangled photons in a reliable way is impossible right now, stalling the development of the optical quantum computers that would use entangled photons as quantum bits (qubits). Because entangled photons can only be produced at random — which takes time — the most powerful optical quantum computing device use only 6 qubits. UK and Israeli quantum physicists have designed a blueprint for a 'quantum machine gun' that fires out barrages of entangled photons on demand. They think within a few years this device will be built, and could lead to quantum computing using 20 to 30 qubits. Every additional qubit doubles the computing power, so these quantum computers could outperform any existing classical computer, the researchers say. The quantum machine gun is described as 'one of the most exciting theoretical proposals I've read in five years' by a leading quantum physicist." The research was published in Physical Review Letters earlier this month.
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A "Photon Machine Gun" For Quantum Computers

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  • by JorDan Clock (664877) <jordanclock@gmail.com> on Monday September 28, 2009 @12:28AM (#29562547)

    Every additional qubit doubles the computing power, so these quantum computers could outperform any existing classical computer, the researchers say.

    But only for probabilistic algorithms. It's not going to be faster at everything.

    • by Tablizer (95088) on Monday September 28, 2009 @01:02AM (#29562681) Journal

      But only for probabilistic algorithms. It's not going to be faster at everything.

      So Whpt if we occjsion?lly fl#p a fwe bits.
         

      • by Canazza (1428553)

        It'll be like a Quantum Rambo. You'll take out a hell of a lot of Scenery with your spray

    • no peeking (Score:5, Funny)

      by RuBLed (995686) on Monday September 28, 2009 @01:15AM (#29562713)

      It's not going to be faster at everything.

      It's going to be faster at everything.

      • yea theyre not going to be able to do anything that a classical computer cant but they will be way more efficient and faster, a lot of military funding going into research they will obviously help a lot with decoding
      • by moon3 (1530265)
        Entanglement switches are rated 10000x speed of light (physics experiment performed in Geneva, Switzerland -- this is from Wikipedia) and upper limit is not even estimated.
        • Re: (Score:2, Interesting)

          by plastbox (1577037)

          One (*err* more) thing I don't get.. How do they know quantum entanglement even happens? They entangle a pair of particles. Then they measure the state of one, causing the other to collapse into the same state with no regard to distance between the two.

          However, as it is impossible to measure the quantum properties of these particles without collapsing them into a non-super state, how do we know that the entanglement wasn't just the two particles gaining the same properties at the moment of entanglement? Obv

          • Re:no peeking (Score:4, Informative)

            by Artifakt (700173) on Monday September 28, 2009 @07:55AM (#29564455)

            First, let's look at a fair attempt to explain why quantum indeterminacy is not just the same thing as classical indeterminacy (like your two particles, which by your question were presumably determinate in the classical model, at least until they became entangled). You seem to be reasoning much as the following note claims early quantum physicists tried to, when they first grappled with Heisenberg's uncertainty principle and the question of knowing the position and velocity of an electron simultaneously. I give you someone deliberately trying to put the concept in normal, natural language and not use any actual math:

            http://www.uhh.hawaii.edu/~ronald/310/Quanta.htm [hawaii.edu]

            One point is, the interpretation that we can't know both position and velocity at the same instant, therefore the electron doesn't have both at the same instant, doesn't explain that thing you refer to as "with no regard to distance". This is what sometimes gets called "Spooky action" and is related to non-locality in general. Starting from the interpretation that it's not our not knowing that causes the indeterminacy but the indeterminacy which causes our not knowing turns out to be putting the horse back in front of the cart. Once people started working from the idea that the indeterminacy is fundamental and not like your example of the balls (where there is a definite color for each, and the observer just doesn't know it yet), they started making progress on figuring out how entanglement could be faster than light.

            http://www.absoluteastronomy.com/topics/Quantum_indeterminacy [absoluteastronomy.com]

            This is about what non-locality really means: One consequence is that we can't assign a local cause (such as: a localized observer hasn't looked yet) to explain why something on the quantum level is determinate, or we lose the ability to explain how the faster than light part happens.

            Just as the original QM problem was about determining position and velocity, talking about "non-localizable" (position), and instantanious/faster than light (velocity) is two ends of the same stick. The more you prove that the action happens much faster than the limitation of light-speed, the more you can't claim the action is caused by anything in a particular locale.

          • by Bakkster (1529253)

            However, as it is impossible to measure the quantum properties of these particles without collapsing them into a non-super state, how do we know that the entanglement wasn't just the two particles gaining the same properties at the moment of entanglement? Obviously, this would result in them having the same properties once measured.

            How do we know that this super state exists, when it is impossible to measure? If a piece of equipment paints two balls a random color and puts them in separate boxes aren't the balls, by the same definition, in a super state as we can't know their color until we open the box? And can they be said to be entangled, as once you open the first box and observe that the ball inside is for example red, the other ball will also be red even though it has yet to be "measured"?

            IANAQP, but this is pretty much correct. For the most part, the particles do get their properties matched upon creation, so your analogy is initially correct. However, the property could be one randomly determined while in the separate boxes, yet the second ball still matches the properties of the first ball after opening. This is basically the 'quantum-ness' that is, in general, incredibly confusing.

            There's a reason even Einstein mocked this as "spooky action at a distance" and said that if it were true

          • Re: (Score:3, Informative)

            by wurp (51446)

            OK, you measure photon phase with a polarized lens. The way you measure the phase is to pass the photon through a polarized lens at an arbitrary angle. Unfortunately, all you can measure about the phase is whether the phase matches that of the lens - either the photon makes it through the lens, which means the photon had the phase of the lens, or it doesn't, which means the photon had a phase at 90 degrees to the lens. There's lots more to say about this, but I think this is enough to explain the answer

          • Re: (Score:3, Interesting)

            by CopaceticOpus (965603)

            The relevant theory here is Bell's Theorem [wikipedia.org] (or Bell's Inequality.) The principle of entanglement has been shown experimentally using some clever approaches based on probability.

            If you measure a specific property of two entangled particles, you are correct in saying that there is no way we could know if the result of the measurement was predetermined. However, experiments were set up in which a large number of pairs of particles were measured. Each measurement recorded one of several possible properties, cho

      • Re: (Score:3, Funny)

        by Anonymous Coward

        It's not going to be faster at everything.

        It's going to be faster at everything.

        It's going to be simultaneously faster and not faster at everything.

    • by physburn (1095481)
      It certainly depends if an quantum algorithm has been made for the problem, thats very hard, and not been done for most things. Most of us have heard that a quantum computer can solve factorisation in order n^3 thanks to Grovners algorithm. While classical computer take exponential time in n. Quantum computers (with Quantum storage), can also search data in a unsorted database table, in order sqrt(n), compared with the classical n. Neither of these are to be sniffed at, a very strong increase in speed. Neit
      • Re: (Score:2, Informative)

        by maxwell demon (590494)

        As far as a know it not yet known if a quantum computer can turn NP complete problems, in polynomial problems at all, or for what problems this is possible.

        Of course, as of yet it isn't even known if a classical computer can calculate NP complete problems in polynomial time. P!=NP is still a conjecture.

        BTW, the correct arXiv reference is arXiv:quant-ph/0601151 [arxiv.org]. After all, there's also astro-ph/0601151, cond-mat/0601151, hep-ph/0601151, hep-th/0601151, math/0601151 and physics/0601151, none of which are rele

    • Every additional qubit doubles the computing power, so these quantum computers could outperform any existing classical computer, the researchers say.

      As all the photons are entangled with the same electron it simply means that 1 qubit is going to be easier to read because it is being represented by multiple photons and an electron the idea that the more photons you entangle the more qubits you get is nonsence because they are all essentially linked so any change on one will be mirrored on the others

  • by religious freak (1005821) on Monday September 28, 2009 @12:30AM (#29562555)

    Every additional qubit doubles the computing power, so these quantum computers could outperform any existing classical computer, the researchers say.

    I thought that the "power doubling" was not in a traditional sense.. the qubit is fantastic at pattern matching and search functions, but no better than a classical computer for something like, say, a video game requiring finite mathematical calculations. I'd state this as a fact, because I've read this in at least a couple places, but seeing as how quantum physicists haunt this forum, I can't say I know as well as them. But this power is only useful in very specific circumstances, AFAIK.

    • Re: (Score:3, Interesting)

      by TubeSteak (669689)

      I thought that the "power doubling" was not in a traditional sense.. the qubit is fantastic at pattern matching and search functions

      Which is all that really matters for breaking encryption, and is the whole reason we have computers in the first place.
      So my question is how many bits of encryption do I need to keep a 20~30 qbit computer out of my truecrypt partition?

      • Re: (Score:3, Informative)

        by MartinSchou (1360093)

        If you are very unfortunate, n qubits can map 2^n -1 bits. -1 because 2^0 = 1, and that'd just be weird.

        If this is the case, then a 6 qubit machine maps 63 bits, but 20 would map 1,048,575 bits (1 Mbit of information) and 30 would map 1 Gbit of information.

        • That doesn't sound right to me. Do you have a citation? Or did you just make that up?
          • I honestly haven't a clue. I just figured that 2^n would give you an exponential power gain to the point where 20-30 qubits would be enough to brute force most types of encryptions.

            If you have a device that can brute force a 1 Mbit to 1 Gbit key in a single step, your regular encryption types are dead.

            But I haven't a clue how it maps from qubit to bit. The maths shown on the Wiki page [wikipedia.org] and on quantum computer [wikipedia.org] is way above my head. The last one notes: "For example, a 300-qubit quantum computer has a state des

        • by sorak (246725)

          And as an additional note, for every ten afterward, you would multiply by roughly a thousand. I.E.

          2^10 = 1,024 b = 1kb
          2^20 = 1,048,576 b = 1mb
          2^30 = 1,073,741,824 b = 1gb
          2^40 = 1,099,511,627,776 b = 1tb

          I suspect this is nothing new to you, but, there are other people who might find it helpful to know.

      • Infinity qubits would be needed if you one time pad your information (essentially doubling the disk space required to encrypt of course).
    • On the other hand, some problems like collision testing are really just pattern matching or search functions, and that has a huge amount of applicability to game design. There are many other similar problems that, at first blush, sound easy, but turn out to be quite difficult, and I've yet to see a modern game with physics that doesn't somehow manage to get objects stuck in floors or falling through levels.

    • Re: (Score:1, Interesting)

      by Anonymous Coward

      Alright, here's how it works: A quantum computer can efficiently execute algorithms the class BQP, which means "Bounded error, quantum, polynomial time". Since all quantum algorithms are probabilistic, "bounded error" means just that - that you can, basically speaking, run the algorithm as many times as you want to get the error as low as you want. Polynomial time means the time you have to wait increases relatively slowly with respect to the size of the input[1].

      What the previous comments seem to be talkin

    • Even if you were right, I'm sure there's plenty of searching and pattern matching in video games. Especially searching.

      Regardless, video games are not nearly as interesting an encryption.
  • Israeli quantum physicists have designed a blueprint for a 'quantum machine gun'

    In other news, Palestinian quantum physicists have designed shoulder-mounted quantum launchers and quantum vests in response.

    Civilians are hopeful for peace and terrified for escalation of hostilities.

    • Re: (Score:2, Interesting)

      by eonlabs (921625)

      It's a sad world we live in, that in the presence of scientific breakthroughs and ingenuity, one of the first thoughts that arises is of the fighting that surrounds that part of the world. I suppose Yom Kippur is a surprisingly appropriate time for reflection on that though.

      • by linzeal (197905)
        I wonder if in 50 years the bad guys in the movies will be more likely to be Israeli or from an Islamic Country.
      • by Rogerborg (306625)
        It would help if they hadn't chosen to call it a "machine gun". What's wrong with "photon ejaculator"? Make love, not war.
        • by bar-agent (698856)

          What's wrong with "photon ejaculator"? Make love, not war.

          Hey, baby, wanna light up your life? Let me shoot my rays into your black hole!
          My light bulb goes in your socket, you cute thing, you, my lamp in your room, you dig?

          Yeah, the innuendo is transparent, better to let my intentions shine through.

    • by Covalent (1001277)
      In other other news, the Trekkies are all thinking about the photon torpedo due to arrive within the next 15 years.
    • by TheSpoom (715771) *

      Meanwhile, a small group of civilians in a nearby town swear that they saw an person in an odd-looking motorcycle zoom past them at high speed the other day, leaving some kind of wall in his wake.

  • Again, Trek predicts the future.

    • ? Trek talked about a quantum computer? I was so young, I might've missed it, but I think you may be mistaken. I don't remember that at all.
      • by Arimus (198136)

        I suspect he's thinking of a photon torpedo rather than a photon bullet... :)

        I do wonder though whether you could also use this photon machine gun to any form of fancy imaging etc...

        • by GaryOlson (737642)
          If you fired enough high energy photons from this gun at a mass of plutonium I think the ensuing explosion would make an image of you on the concrete wall! Is that fancy enough?
  • by Tastecicles (1153671) on Monday September 28, 2009 @01:23AM (#29562745)

    imagine a Beowulf cluster of... NO! NONONO!

    • Re: (Score:2, Funny)

      by Yoozer (1055188)
      I tried to imagine a cluster of photon machine guns and all I could come up with was a container full of Mag-Lites.
  • say hello to my little friend... (Please try to keep minds out of the gutter if possible)
  • Ok, so on this site bursting with intelligent, educated folk, the following question(s) might make me look like a village idiot, but what the hell. It's damn interesting stuff and I want to know!

    Exactly how does quantum computing work? I have a fleeting grip the basic stuff; qubits existing with states 0, 1 and "superposition" (i.e. all possible states) and that by actively measuring it's state (sending a photon or whatever bumping into it) you collapse it, and it's entangled mate, into a "classical state".

    • by noundi (1044080) on Monday September 28, 2009 @02:16AM (#29562935)

      Ok, so on this site bursting with intelligent, educated folk...

      You lost me at "Ok".

    • by maxwell demon (590494) on Monday September 28, 2009 @03:52AM (#29563267) Journal

      Ok, I just wrote a lengthy reply, and then by accident hit "refresh", and all the text was gone :-(

      Therefore here the short version:

      • The speedup is basically because for quantum systems the dimension of the configuration space grows exponentially rather than linearly with the size of the system (i.e. number of qubits). The fact that we can't simply measure the complete state is actually a limitation, because it means we cannot directly access an arbitrary unknown state.
      • You can do quantum computing by just doing measurements because every measurement modifies the measured system, and with entangled states, this change is non-local (i.e. you also modify parts of the system where you didn't just destroy any entanglement by your measurement). However you need special entangled states to do universal measurement-based quantum computing (i.e. to allow arbitrary transformations with measurement only); one state which works is the cluster state produced by this "photon machine gun"
      • They didn't claim that qubits revolutionize storage, but that if emulating the 20 to 30 qubit quantum computer on a classical computer, it would not fit into computer storage. However I doubt that; storing the state of 30 qubits needs about 16 GB, which is large, but perfectly doable in todays computers (and may be actually standard by the time this photon gun is realized). The problem with simulating the quantum computer would not be storage, but time.
      • storing the state of 30 qubits needs about 16 GB, which is large, but perfectly doable in todays computers

        I can haz ur USB for teh ReddyBoozt?

        kthxbai.

      • I checked the patent in your link. It was re-examined in 2003, and all claims canceled. Whew, my kids are safe.
      • Re: (Score:3, Informative)

        by noundi (1044080)

        Ok, I just wrote a lengthy reply, and then by accident hit "refresh", and all the text was gone :-(

        You're welcome. [mozilla.org]

    • Re: (Score:3, Informative)

      by Anonymous Coward

      Bad analogy time.

      The simplest way to factor a large number is to just try to divide it by 2, by 3, etc. Once you've divided it, you now have 2 smaller numbers to factor. Repeat until you get a prime. This takes a long time for a large number because you have to try it over and over again.

      With a quantum computer you can do all of these computations in parallel, and then arrange for all of the non-factors to cancel each other out, meaning that you can only measure a legitimate factoring. (Getting all of th

      • by plastbox (1577037)

        Thanks for the long reply, but I don't think you got the whole "me being the village idiot"-part. Your post doesn't really impart any understanding of a qubit as a computational unit. =/

        Yes, I understand the benefits of parallel processing. Hook up huge number of MUC's, send every MCU in "level 1" the same number, have MCU nr. 1 divide the incoming number by '2', MCU nr. 2 by '3', and so on, and pass on only the results that are whole numbers to the next level. Lather, rinse and repeat for however many step

      • The quantum algorithm for factoring does not just divide repeatedly "in parallel." Shor's algorithm really describes a specially built machine for factoring (which converts factoring to period finding, and a fourier analysis is forced and sampled).

        In fact, I first studied Shor's algorithm in order to understand why good programmers weren't looking at it, generalizing it, and writing a million more algorithms. I was disappointed to learn that we are not far enough along to describe a universal quantum c
    • by tehcyder (746570)

      Ok, so on this site bursting with intelligent, educated folk

      I hope (for your sake) you're being sarcastic.

  • It's called a "Strobe Light", stupid.

    I know.....bad joke.....

  • Say flashlight.
  • Dirty Erwin (Score:5, Funny)

    by ciderVisor (1318765) on Monday September 28, 2009 @05:21AM (#29563635)

    I know what you're thinking: "Did he flip six qbits or only five?" Well, to tell you the truth, in all this excitement I kind of lost track myself. But being as this is a Photon Machine Gun, the most powerful quantum entanglement source in the world, and would blow your head clean off, you've got to ask yourself one question: Is the cat dead or alive ? Well, is it, punk ?

  • Heh (Score:5, Funny)

    by L4t3r4lu5 (1216702) on Monday September 28, 2009 @07:06AM (#29564129)

    The quantum machine gun is described as 'one of the most exciting theoretical proposals I've read in five years' by a leading quantum physicist.

    The long winter nights must just fly by.

  • So... Is "photon machine gun" another would for a light bulb?
  • I wonder if this is inherent in the universe representing some absolute barrier to doing Quantum Entanglement computations, 'Yes the universe will do your computation instantly, but not until you provide umpteen zillion entangled qbits. The universe will take 10^100 years to aquire sufficient randomness, please use /dev/urandom for quicker testing.
  • Now where am I going to find a quantum Bikini Girl to fire my quantum machine gun?

  • IA Quantum Uzi's for sale, free with a new car.....
  • I would like to know because if it gets tied into the main deflector array it could cause a metreon cascade in the warp core's plasma injectors.

  • How good would quantum computers be for raytracing (particularly of the hard-core globally illuminated variety) ?

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