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Quantum Computer Works Better Shut Off 376

Posted by Zonk
from the oh-my-head dept.
waimate writes "A New Scientist article relates how its possible to get answers from a quantum computer even when your program isn't running." From the article: "With the right set-up, the theory suggested, the computer would sometimes get an answer out of the computer even though the program did not run. And now researchers from the University of Illinois at Urbana-Champaign have improved on the original design and built a non-running quantum computer that really works."
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Quantum Computer Works Better Shut Off

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  • Gee whiz (Score:4, Funny)

    by JPamplin (804322) on Thursday February 23, 2006 @09:18AM (#14784121) Homepage
    Wish I could do that with my "real" PC - save alot of power that way. Hard to see the screen though. ;-)
    • Re:Gee whiz (Score:3, Funny)

      by BobPaul (710574) *
      It reads to me like the computer isn't off, just the search program isn't running. Unless whatever optical sensors they're using to get they're answer aren't considered part of the computer.

      I'll admidt I really don't understand what the article is talking about, but I'm pretty sure it has something to do with Heisenberg's Uncertainty...
      • I guess in theory it's to do with the "While it's off in *this* place, it could be on in *that* place, and that means *that* one could've run the program".

        Or something.

        However, first thing I did was check that it wasn't dated 1st April...
      • Re:Gee whiz (Score:5, Funny)

        by flyingsquid (813711) on Thursday February 23, 2006 @09:49AM (#14784399)
        I'll admidt I really don't understand what the article is talking about, but I'm pretty sure it has something to do with Heisenberg's Uncertainty...

        This sounds like zen buddhist computer science. Either that or something cooked up after a little too much of the green stuff. Still, makes me wonder. What kind of software do you run... erm, not run... on a computer that isn't running? Non-existent programs, like Duke Nukem Forever?

        Hrm. That would open up a whole new industry. That'd be a fun profession, full-time vaporware programmer... hell, I'm gonna start right now. I'm officially announcing VaporWorks, an integrated word processor, spreadsheet, calendar and presentation software suite, not running on your computer in the near future. If anyone needs me, I'll be on the beach in Cancun spending my startup money, not busy working 16 hour days to get it ready.

        • Re:Gee whiz (Score:3, Funny)

          by PFI_Optix (936301)
          VaporWorks 2.0 should integrate a media player, photo editor, and its own integrated web crawler to compete with Google.

          After all, it's always best to try to make your product do everything, even if it sounds impossible. Apparently VC investors like that.
        • by LandKurt (901298) on Thursday February 23, 2006 @10:09AM (#14784592)
          If anyone needs me, I'll be on the beach in Cancun spending my startup money, not busy working 16 hour days to get it ready.

          No, here's what you do. You build a shielded, sound proofed room with your computer workstation, a nice entertainment center, bar and comfy recliner. Then you seal yourself in the room so no one can tell what you're doing. Either you have the computer turned on and are hard at work programming or you're kicked back doing nothing enjoying yourself. Call it Schrodinger's programmer.

          Now, if your computer is hooked up to the Zeno effect device described in the article, it should be able to read the results of your work whether you actually did it or not. This should usher in a revolution in work environment for programmers everywhere.

        • Re:Gee whiz (Score:4, Funny)

          by Wilson_6500 (896824) on Thursday February 23, 2006 @01:22PM (#14786462)
          Too late. I hold the patent on all non-running software. You either must pay the monthly licensing fees for not running my software, or purchase and run my software, which itself requires the additional purchase of monthly update packages.
        • Re:Gee whiz (Score:3, Informative)

          by kalirion (728907)
          What kind of software do you run... erm, not run... on a computer that isn't running? Non-existent programs, like Duke Nukem Forever?

          No, you can't run non-existent programs (i.e. those who have 0% chance of existing.) However, the quantum computer would be able to run a program that has a non-zero waveform. I'm assuming this computer would be similar to Discworld's Hex [wikipedia.org].
      • With this computer you can play the new Duke Nukem 10x faster even though it's turned off. On the second thought, you can do the same with your computer at home, just close your eyes and focus...
      • by saskboy (600063) on Thursday February 23, 2006 @10:24AM (#14784737) Homepage Journal
        New business model:
        1. Buy super quantum computer
        2. ???
        3. Profit!

        We now know step 2. Shut the computer off and go for a long weekend.
      • Re:Gee whiz (Score:5, Insightful)

        by radtea (464814) on Thursday February 23, 2006 @10:25AM (#14784745)
        I'll admidt I really don't understand what the article is talking about,

        Neither did whoever wrote the article.

        It works like this:

        1) Define some classical terms, like "running" and "actually"
        2) Apply them incorrectly to quantum situations
        3) ob. ????
        4) Profit!

        The components of the photon wavefunction that are "not actually running the program" become entangled with the components of the photon wavefunction that "are actully running the program", and therefore they carry information regarding the state of those components.

        If we think about this in classical terms, where we incorrectly and falsely imagine that each component of the wavefunction represents a classical trajectory through the apparatus, we could incorrectly and falsely say that photons that have not followed classical trajectories through the part of the apparatus that does the quantum computation have not run the program.

        But the clear contradiction of that statement makes the slippery bullshit marketing-speak of the article clear: of course a photon that has followed any classical trajectory whatsoever has not run the quantum program. And to claim that "a photon whose wavefunction is entangled with the program has not run the program" too obviously has the same epistemological and moral status as giving away "free" products that only require a "small" processing fee to claim.

        One is motivated to ask, "Why doesn't entanglement with the program state count as 'really' running the program? What is this 'real' thing you keep talking about?" Admittedly, entangling things in this way is a different way of running the program, and is really rather clever, but to promote the results in this way is just attention-grabbing marketing, unworthy of the name of science.

        This kind of abuse of language is similar to that of the "quantum teleportation" folks, whose deliberately misleading claims often make it sound like something other than the ontologically-problematic quantum state is being "teleported."
        • Re:Gee whiz (Score:3, Insightful)

          by waxigloo (899755)
          First of all: Profit? These are university physicists, not a company trying to trick you into buying something. The most they profit will be a pat on the back from the physics community.

          Second: you clearly don't understand the experiment, so why accuse the authors of 'bullshit marketing-speak'? 'On and Off' are not necesarily classical notions; the method to implement on and off is quite simple -- you just use a beamsplitter.

          You also seem to have the impression that just because two photons are entan

  • by SomeoneGotMyNick (200685) on Thursday February 23, 2006 @09:19AM (#14784123) Journal
    I sometimes get better answers to my own questions simply by sleeping on it.

    • That reminds me of an old study technique I used to recommend for folks who were well and truly screwed the day before a test.

      I also relies on the quantum properties of brain matter.

      Here is how it works:

      Step 1. You take your text book and open it to the middle of the section you need to know for tomorrow.

      Step 2. Insert a bookmark into this spot (not a scrap of paper, a bookmark) and close the book around it.

      Step 3. Place the book + bookmark under your pillow.

      Step 4. Sleep on it.

      Step 5. When you rise (fully
  • by Rob T Firefly (844560) on Thursday February 23, 2006 @09:19AM (#14784124) Homepage Journal
    Neat! It's an updated Sinclair ZX-81!
  • ...works so much better when turned off.
  • Oh What Fun (Score:2, Funny)

    by TechJones (781168)
    Think of all the power we would save not playing MMOs with the PC turned on.
  • This scheme could have an advantage over straightforward quantum computing. "A non-running computer produces fewer errors," says Hosten. That sentiment should have technophobes nodding enthusiastically.

    Duh! It's not running so it can't produce errors! :)
  • So... It's running Windows? Hey, stop hitting me!

    Seriously though, this statement made my day: "A non-running computer produces fewer errors," says Hosten.

    How do I convince my boss that I can work this way, too?
  • How better to prove that your invention is useless than to have it be just as useful when shut off? That's gotta suck!
  • Hang on.. (Score:2, Funny)

    by cameronking (914247)
    <sarcasm>
    How can it work better when its off than when its on. Its either on or off, it can't be on and off at the same time!
    </sarcasm>
    • by sczimme (603413)

      How can it work better when its off than when its on. Its either on or off, it can't be on and off at the same time!

      Schroedinger + Heisenberg == Schroedenberg's Uncertain Cat Principle

  • The computer says the answer is 42.

    All we need to do now is program the question...

    Z.

  • You mean like us? (Score:3, Interesting)

    by aliens (90441) on Thursday February 23, 2006 @09:25AM (#14784174) Homepage Journal
    Ever hear the expression "I'll sleep on it" ?

    I've read several times how not thinking about a problem will lend itself to a solution.

    ie Go take a walk, get a cup of coffee, take a nap.

    Interesting, or maybe I just need coffee.
  • by G4from128k (686170) on Thursday February 23, 2006 @09:26AM (#14784179)
    Soon there will be quantum malware that "runs" even if you never try to open it, even if you kill its process, even if you filter it, even if your packets just pass close to it.

    For all we know this malware is already running.
    • by timster (32400) on Thursday February 23, 2006 @09:43AM (#14784351)
      Yeah, I can see it now:

      "You imbecile! You let that virus infect our systems!"
      "But I didn't open the file!"
      "Yes, but there was a 2 percent chance that you would have, so two percent of our data was affected... and included in that two percent was your entry in the payroll database. So I'm not firing you, but you won't be paid anymore."
      "This sucks! I'm going to commit Schroedinger's Seppuku! You'll regret this when I walk in that door with my guts both spilling out and in my body!"
  • and... (Score:5, Funny)

    by jcostantino (585892) on Thursday February 23, 2006 @09:26AM (#14784181) Homepage
    in unrelated news, my refrigerator light bulb works better with the door closed.
  • But how do we KNOW it's off?
  • Misleading (Score:5, Informative)

    by karvind (833059) <.moc.liamg. .ta. .dnivrak.> on Thursday February 23, 2006 @09:27AM (#14784185) Journal
    Running in quantum computers is doing "unitary transformations [wikipedia.org]" and doing measurements on them. So as the article claimed, it is not that you are not doing anything. The only way not to run "it" is by putting it in eigenstate of the system (as well completely isolate it from any external perturbations). If you put it in a mixed state - yes it will evolve with time and then when you do the measurement it will give you "a" eigen state with certain probability. So yes in the end you are still doing measurement which is equally important and consitutes "running" the computer.

    Does anyone know what is new here ?

    • Re:Misleading (Score:4, Insightful)

      by tbo (35008) on Thursday February 23, 2006 @01:49PM (#14786708) Journal
      Disclaimer: IAAQIS (I Am A Quantum Information Scientist).

      The actual journal article that New Scientist is referring to was just published: Nature 439 949 [nature.com]. I'm not sure if that link will work if you're not at an institution that has a subscription, but you'll probably at least get to see an abstract.

      A few bits of background: New Scientist's coverage of quantum information is sometimes horrible. Therefore, it's not surprising that the New Scientist article makes no sense but contains lots of exciting fluff. That said, these guys do have something interesting.

      I skimmed through the Nature article, and it looks interesting. It's especially nice that they have an experimental implementation. Nonetheless, the bit about the quantum computer being "off" is just silly.

      Here's a summary of how it works, stripped of some hyperbole and converted into something more like plain english (note: qubit means quantum bit).

      (1) Create a "control qubit" and some output qubits, with the control qubit initially set to 0, which we will take to mean off.

      (2) "Rotate" the control qubit into a superposition of 1 (on) and 0 (off), with most of the "amplitude" being for the 0 state (the qubit is mostly off)

      (3) Apply whatever algorithm to the data and the output qubits, conditional on the control bit being on. (Note: we don't actually measure anything here--this is entirely a unitary operation).

      (4) Perform a weak measurement on the output qubits, which has the effect of reducing the amplitude of the output qubits being in something other than their initial state (which can only happen if the control qubit was on and the algorithm was applied), since the amplitude for that was small to begin with.

      (5) Repeat (2) - (4) N times, such that, if the output bits are unmodified after each algorithm application, you end up with the control qubit in the 1 (on) state. Otherwise, you get the 0 (off) state.

      (6) Profit!

      This is the simple version, in which you only get to learn whether the application of the algorithm to the data gives you the default output or not. There's a more sophisticated version in which you learn more about the data.

      There are a few catches here. One is that N has to be reasonably large, or the probability of an "error" in step 4 becomes an issue (by error, I mean that the weak measurement gives us the wrong outcome). Specifically, the probability of an error is 1 - cos^2N (pi / 2N), which scales as O(N^(1-4N)). Fortunately, that is exponential suppression of error, which is pretty good scaling. Another catch is that their particular experimental implementation used a non-scalable encoding. This isn't a major issue, but it means we should wait for an experiment using a scalable encoding before we really break out the champagne.
      • Re:Misleading (Score:3, Interesting)

        by bughunter (10093)
        New Scientist's coverage of science is typically horrible. Therefore, it's not surprising that any New Scientist article makes no sense but contains lots of exciting fluff.

        There. Fixed it for ya.

        Ever since Scientific American went pop-sci in the mid-90's, we've been without a decent, objective layman's science magazine that avoids sensationalising.

        Science News weekly is probably the best, but it's written for a 10th grade audience.

  • Laziness... (Score:5, Funny)

    by bwcarty (660606) on Thursday February 23, 2006 @09:27AM (#14784187)
    I may appear lazy, but on a quantum level, I'm really quite busy.
  • by Lxy (80823) on Thursday February 23, 2006 @09:29AM (#14784200) Journal
    Microsoft reported earlier today that Windows performs better with your PC shut off.
  • I always thought programming was more art than science, and a dark art at that. This proves that at it's best computers are magic. Soon they'll have computers that give their answers even if it hasn't been programmed, or better yet even if it hasn't been built yet. Those answers will be the most accurate of all!

    When does stuff like this make people start to lose credibility? Are we there yet? IANAQM, but on a simple gut level I can't buy any of this.
    • Re:Black Magic (Score:5, Informative)

      by MindStalker (22827) <mindstalker AT gmail DOT com> on Thursday February 23, 2006 @09:57AM (#14784477) Journal
      If you read the description its not actually as wrong headed as it sounds, the whole "its not running" thing is really inacurate. Basically they have a "program" that does a database search, this "program" is actually physical hardware that is run by optics. They "ran" it by shooting a photon at it, but then blocking the photon before it entered the program thus it "not running". The trick is that properties of the photon continued into the program and it worked. This really isn't new news for anyone who has every dealt with the slit experiment or any number of experiments that show that photons can be in multiple places at once.
  • ...The next generation will give correct answers before it's even built.
    • to either complain about the results version 2 will produce or not. Then, I may or may not have suggested that we not build the version 2 at all which may or may not have resulted in the version never existing. Then the universe imploded. Fortunately, that was the OTHER universe.
  • "the computer would sometimes get an answer out of the computer even though the program did not run."

    sounds like another answer to a question no one asked.
  • by Rick.C (626083)
    So that's why Deep Thought forgot the question! It was turned off for all those millennia while it worked on the answer.
    • Damn, I was just about to make a 42 reference! I will have to go back and think of a joke as to why it would result in 42.
  • Running or not? (Score:2, Insightful)

    by papaballoon (946842)
    Maybe we should look at what the definition of running is for a Quantum computer. Once it is assembled is it at that point running? Are applications an add on for functions pertaining to specified data?
  • Am I the only one who read that headline and thought of John W. Campbell's infamous Hieronymous machine? [wikipedia.org] Instead of a circuit board, the machine would have a diagram of a circuit board...and still work.

    Naturally, no one has ever been able to reproduce Campbell's results. Campbell was a great science fiction editor, but a real crank when it came to crackpot psuedoscience.

  • by the eric conspiracy (20178) on Thursday February 23, 2006 @09:31AM (#14784230)
    I can just see the next article - "Quantum Software Works Better Without A Computer".

    And the followup:

    "Quantum Software Works Better Before Writing the Code Than After Writing the Code".

    • "Quantum Software Works Better Before Writing the Code Than After Writing the Code".

      So Quantum == Microsoft?
    • "Quantum Software Works Better Before Writing the Code Than After Writing the Code".

      Actually, that's what Microsoft software does. Remember how great WinXP was before anybody seen it?
  • ...If you don't open the box and look inside? I mean, without peeking and knowing for sure, it's in an indeterminate state.
  • Now you can tell whether the cat is dead regardless of whether the cat is dead or not.
  • Did Bloody Stupid Johnson [wikipedia.org] have anything to do with this? If so, it sounds an awful lot like he used a few lessons he learned from his work on the Post Office Mail Sorter and the New Pie [wikipedia.org]

    Three and a bit. You gotta have it.
  • I have a quantum clock on my desk that is shut off, too. It is exactly correct twice a day.
  • Anybody wanna bet the reasons behind the Black Mesa incident?

    The last of the voice logs from the test chamber read:

    "Shutting down. No. Attempted shutdown! It's not... it's not... it's not shutting down!"

    Wanna bet why?
  • I've come to the conclusion that quantum scientists go out of there way to describe everything in confusing and fantastic terms. Obviously this "computer" is running. It's not like they turned it off and came back in the morning and the "answer" had magically appeared. They may think that all the photons are being captured and so none of them ever enter the "computer" itself. But the work is getting done, so something must be traveling through the "computer". If they don't know what that something is, it do
  • It is still running in a sense (ie. it has power and "stuff" is happening). Just not the typical sense for a quantum computer.

    Seems stupid to suggest it's "shut off" because it's not. I would consider "shut off" would mean it has no power flowing to it.
  • I swear my watch says February 22 not April 1!
    • Considering it's the 23rd, and this story was posted on this same date, I'd say you've got one of those weird quantum-calendars. May I suggest buying a Casio or Rolex? ;)
  • A Quantum computer is never really on or really off - it's relatively a little bit off and on at the same time!
  • Now if they can get it to think of your questions for you it'll be perfect.
  • improving your error rate by turning the machine off is easy if you're wrong with high enough frequency....
  • rand() even happen to give me the correct answer before I ask the question !
  • Further evidence that time and space is an illusion. Nothing really exists. Anything is possible except waking up. Rod Sterling [would be => is => will be ] proud .
  • by Otter (3800) on Thursday February 23, 2006 @10:01AM (#14784509) Journal
    I've read the linked article, the commentary article in Nature and the Paper itself, and am completely mystified as to what they're claiming. As best as I can tell, they subsetted their data and found that the (rather misleadingly named) "non-running" events were more informative than the set as a whole.

    Coming back here, the discussion consists entirely of moronic comments about Windows. Would someone with a clue care to provide some useful commentary?

    • No problem. The concept of "counterfactual computation" the article refers to is based around the ideas of the Elitzur-Vaidman bomb testing problem [wikipedia.org]. Imagine you have a computer with an on/off switch. If it's a quantum computer, then it's possible to put the switch in a superposition of both "off" and "on". If you try to read the switch, you'll always see "off" or "on"; however, it's possible to run an algorithm on the quantum computer that preserves this combination of "off" and "on". Using clever quantum i
      • Thanks!!! That's very helpful. Two questions, though:

        1) In the Elitzur-Vaidman thought experiment, which part corresponds to the on-off switch?

        2) Is the "non-running" experiment physically performed differently from the normal method, or is it a refinement made in the data?

        • >1) In the Elitzur-Vaidman thought experiment,
          >which part corresponds to the on-off switch?

          The entire computer takes the place of the bomb(s). The "on-off switch" is really whether or not a photon enters the computer (thus running the program).

          >2) Is the "non-running" experiment physically
          >performed differently from the normal method,
          >or is it a refinement made in the data?

          The "experiment" only works when it is running. What's "non-running" is the computer, or perhaps more precisely, the co
  • OK, I freely admit that the science behind how a quantum computer works is WAY beyond me, so correct me if I'm wrong about this. Wouldn't the ability to run a program without the computer being in an active state mean that quantum computing is an insane security risk? The article mentioned that they believed they had to specifically build the computer to exhibit this strange (and frankly fascinating) property, so does that mean this particular feature can be designed out?

    I'm not talking about "quantum cry
  • ..did it also deduce the existance of rice pudding and income tax?
  • Was there an article a while ago about complex decision are better made when sleeping? I can work in the future with my computer off and asleep at my desk. The future looks bright.
  • Okay I read the article and don't understand how this works. No one else on Slashdot has posted an explenation of how this works. Can some one please elaborate on this post? All I see right now is stupid jokes...... Which may mean that slashdot operates like the quantum computer. It all makes sense now....
  • This is straight out of Douglas Adams.
  • I think this is the best example that we are actually living in a virtual, simulated universe and the programmers still have a few bugs to work out. It's the bloody Matrix but without all the cool clothes...
  • I do not have a clue, netiher does any of the replies above (e.g: "Windows runs better when turned off"): many "funny" messages, but no "informative" ones.

    Got d***n it. I've read the article (yes I did), I also had in introductory quantum phycics course in undergrad, but I still do not understand "how this is supposed to work".

    Yes they say that using the Schrödinger's idea, they send a photon into the computer while inhibiting it by using a series of mirrors. This rises the photon into a "superposition
  • Nature (Score:3, Informative)

    by Anonymous Coward on Thursday February 23, 2006 @10:17AM (#14784658)
  • by Expert Determination (950523) on Thursday February 23, 2006 @10:39AM (#14784876)
    I remember swapping a few emails with the author of a paper on this about ten years ago. Essentially you can get the result of the computation and yet the computer that runs destructively interferes with itself so that it essentially it remains unchanged at the end of the computation.

    But this doesn't buy you anything. Quantum computers are reversible meaning they use no energy. And the computer has to spend just as long "doing nothing" as it would have spent doing the computation. And your computer is still tied up "doing nothing". So it's basically useless.

  • by SirBruce (679714) on Thursday February 23, 2006 @10:50AM (#14784995) Homepage
    I am not a physicist, but I did spend a couple years in college studying it with an intent to become one, and I still maintain a layman's interest in the subject. Unfortunately, the math is beyond me. In any case, a lot of people are confused how this "works", and so I thought I'd try to help.

    Someone else already posted an useful background URL with is a good place to start:
    http://en.wikipedia.org/wiki/Elitzur-Vaidman_bomb- testing_problem [wikipedia.org]

    Basically, what you have here is something called "interaction-free measurement". Because of the quantum mechanics work, a particle's wavefunction evolves in a certain way over time, which then "collapses" when you measure it to something specific. How it evolves is not deterministic, but probabillistic. Because of this, you can set up a quantum system whereby when you place a certain object in it at a certain place, you can change the whole system given the nature of what you add to it.

    In this case, you have a quantum computer composed of mirrors that runs on photons. The mirrors are pre-set in a certain configuration to run a certain "program". No electricity is needed to "run" the program; you just inject photons into it and it spits out results when you measure it.

    What they've done here is then place that computer in a certain location in an existing quantum mechanical system, the one which the photon comes from. This photon is associated with its own set of mirrors and detectors, and because of where and how the computer is placed into it, it effects the larger system.

    Thanks to QM, you can then tweak the exterior system so that the chances of a photon ever actually getting to the quantum computer are infinitessimally small. But because there's still a small chance, the very nature of the computer in that location allows you to determine the results it would generate, even though a photon never actually gets into it to "run" it.

    So, it's not to misleading to say the program never actually "runs". And you could say the computer isn't "on", but since it's just a mechanical-optical construct it's always "on". More importantly, though, is that exactly where the "computer" is becomes blurred; while it's true that it's particular programming is self-contained, by hooking it up to the external quantum system, you're sort-of making it a part of the computer as well. The "work" is being done by the photons outside the computer; remove them and you don't get anything.

    Wow, reading the above, I didn't really do a good job of explaining this at all. But basically, even though the quantum program never actually executes, you still need to create it, and you still need to put it in a certain spot so that its quantum effect on the world around it can still be measured, and from that, you can infer what the program would actually do.

    Bruce
  • by oGMo (379) on Thursday February 23, 2006 @10:58AM (#14785072)
    Better article. [uiuc.edu] Whoever wrote the other articley looks like they poorly summarized this one. Then the summary for the slashdot posting poorly summarized that. Sheesh.
  • by bnenning (58349) on Thursday February 23, 2006 @01:37PM (#14786599)
    At last we see the purpose of the is_computer_on() [tycomsystems.com] function.
  • by HermanAB (661181) on Thursday February 23, 2006 @05:30PM (#14788555)
    Given the wide spread infestations of malware, most Windoze machines also work better when turned off...

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