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Science Hardware

Schrodinger's Cat Closer To Reality? 59

Posted by simoniker from the mew-mew-mewmew dept.
Shipud writes "A group from the University of Oxford is proposing a scheme to achieve quantum superposition in a large object, according to Nature - not as large as Schrodinger's cat, but about ten-thousandth of a square millimiter, some 10^14 atoms. Quantum superposition is the phenomenon in which a photon passing through a beam splitter to takes two paths at once, inconceivable in the macroscopic world. William Marshall and co-workers suggest to mount a tiny mirror on a springy arm, so that the power of a single photon will be enough to oscillate it. When that photon is superposed, it transfers its superposition to the mirror, which will be quantum superposed: at two places at once. Wave particle duality has already been shown in Buckminster fullerenes, a 60 atom compound. Are we getting closer to quantum computers?"
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Schrodinger's Cat Closer To Reality? More

Schrodinger's Cat Closer To Reality?

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  • Yeah... (Score:3, Interesting)

    by Kiriwas ( 627289 ) on Thursday October 02, 2003 @03:34AM (#7111603) Homepage
    Achieving superposition is great, but how long is it maintainable? To get truly useful quantum computers, we need states that can be maintained that way, for longer periods of time (or so at least some proposed versions say). fp?

    • Re:Yeah... (Score:3, Insightful)

      by drkich ( 305460 )
      The researchers propose to calm this stormy background by cooling the apparatus to less than two thousandths of a degree above absolute zero. The mirrors would also be in a very high vacuum so as not to be disturbed by colliding gas molecules.
      It does not sound like it will be in a case near you any time soon.
      Plus it will be in a high vacuum, not a perfect vacuum. So even though the probability of the mirror hitting any gas molecules is low, how reliable are their results?

      • Re:Yeah... (Score:3, Informative)

        by Jerf ( 17166 )
        So even though the probability of the mirror hitting any gas molecules is low, how reliable are their results?

        All experiments have a reliability less then 100%. Techniques to handle that have been around for a long time.

        Rest assured the experiment will be performed many, many more times then just "once". (It seems to me you have that as part of your mental image.) Supercollider experiments are run into the hundreds or thousands of times (not certain, not part of that community, could easily be millions

    • Re:Yeah... (Score:2, Insightful)

      by Nickybob ( 683407 )
      I don't mean to be a spoil sport, but even if they accomplish superposition, we still have Heisenberg to consider, right?
    • a photon passing through a beam splitter to takes two paths at once, inconceivable in the macroscopic world

      Forgive me if I'm being dense, but don't all particles and waves travel all possible paths all the time? It was my understanding that when a photon travels from point A to point B it does so using every possible path until the waveform coalesces. This works for electrons as well, due to wave-particle duality. I think I disagree with the poster that this *does* actually happen in the macroscopic w
      • but don't all particles and waves travel all possible paths all the time? It was my understanding that when a photon travels from point A to point B it does so using every possible path until the waveform coalesces.

        Ok, my turn to be dense. Aren't you referring to the fourth dimension? A given object/particle will fill every point between its start and its destination. The only reason these points don't collide is that they are plotted along the forth dimension instead of the third. The third dimension is
      • It was my understanding that when a photon travels from point A to point B it does so using every possible path until the waveform coalesces.

        The Path Integral interpretation says that the photon travels every possible path if you do not meausure it while is traveling. The double-slit experiment, in this case, can be understood as limiting the possible paths to only 2 at a particular line (you assume it can only go through one slit or the other).

    • Achieving superposition is great, but how long is it maintainable?

      I've heard yoga and meditation can help.

  • Can they... (Score:3, Funny)

    by drkich ( 305460 ) * <{moc.liamg} {ta} {enilhcikd}> on Thursday October 02, 2003 @03:34AM (#7111605) Homepage
    I would love to be able to stay up really freakin' late and sleep at the same time. Now that would be a break through!
    • I can do that while coding college projects. Come to think of it, quantum logic might have something to do with the results, like when I spot awful pieces of code that I would swear I didnt write.
  • Are we getting closer to quantum computers ?

    Well, that question can only be answered by a quantom computer :(

  • Interesting! (Score:5, Funny)

    by floydigus ( 415917 ) on Thursday October 02, 2003 @04:17AM (#7111756)
    Quantum superposition is the phenomenon in which a photon passing through a beam splitter to takes two paths at once, inconceivable in the macroscopic world.

    Whereas Slashdot is the phenomenon in which a sentence takes two paths at once.

  • Open the box and see (Score:5, Funny)

    by Dancin_Santa ( 265275 ) <DancinSanta@gmail.com> on Thursday October 02, 2003 @04:17AM (#7111759) Journal
    Are we getting closer to quantum computers?

    Maybe.

  • Closer to reality? (Score:4, Insightful)

    by henrygb ( 668225 ) on Thursday October 02, 2003 @05:59AM (#7112017)
    Not until they have done the experiment.

    This is a hypothetical experiment at this stage. Until they actually try, they will not know if they can actually detect the effect of "the system [cycling] back and forth between a superposition of photon states (in which case one can detect an interference pattern) and a superposition of mirror positions (for which there is no photon interference pattern)." It is possible that it cannot be detected (either since observing whether or not there is an interference pattern may destroy the cycling process or because the cycling is not happening at all), in which case it becomes a philosphical question rather than a scientific one.

  • Great, not only can we have quantum computers that calculate all the possible answers at once, but now that we can superpose mirrors,we can display them *all at the same time*!

  • Canonical answer (Score:5, Funny)

    by jolshefsky ( 560014 ) on Thursday October 02, 2003 @07:44AM (#7112258) Homepage
    The question:

    Are we getting closer to quantum computers?

    The answer:

    Yes and no.

  • Obligatory quote (Score:3, Funny)

    by ManxStef ( 469602 ) on Thursday October 02, 2003 @08:21AM (#7112395) Homepage

    inconceivable in the macroscopic world.

    You keep using that word. I do not think it means what you think it means.

  • heating up counts as a measurement (Score:4, Interesting)

    by QEDog ( 610238 ) on Thursday October 02, 2003 @08:32AM (#7112450)
    The cantilever (vibrating arm) is connected to something (the outside). Even if you cool it down a lot, to prevent thermal effects from the outside, the vibrations of the cantilever will heat up the system, and this counts as an observation. The paper doesn't mention how to correct this.

    • Re:heating up counts as a measurement (Score:4, Insightful)

      by radtea ( 464814 ) on Thursday October 02, 2003 @09:37AM (#7112906)
      This is a good point, but I'm sure the researchers have considered it. The limiting factor will be inelastic flexion of the cantilever, which can be made small in a number of ways, not least of which is keeping the amplitude of vibration small. Given that they're talking about setting the thing vibrating using the momentum transfer from a single photon, this shouldn't be a huge problem!

      But it does bring up an important common misunderstanding that the headline of the article repeats: quantum effects have absolutely nothing to do with size and everything to do with complexity. A photon that passes through both slits of a double-slit apparatus demonstrates quantum effects on a scale of a fraction of a millimeter (the separation distance of the slits) and large multi-path interferometers of one kind or another involve photons that take paths that are tens of centimeters or more apart.

      Size doesn't matter. What matters is the number of modes available, because interference between modes destroys our ability to observe quantum effects. Systems of many particles (particularly at higher temperatures) have so many modes available that the coherence time is extremely small, although even then we can under the right circumstances observe things like the Mossbauer Effect [wikipedia.org] in which an entire block of material acts as a single quantum-mechanical entity.

      --Tom
      • This is a good point, but I'm sure the researchers have considered it.

        The paper doesn't address this issue, nor the references.

        The limiting factor will be inelastic flexion of the cantilever, which can be made small in a number of ways, not least of which is keeping the amplitude of vibration small.

        Even if you use small amplitudes or an almost ideal cantilever, the cantilever is still part of a bigger system with a thermal source (the outside, infinite degrees of freedom, yaddy yaddy yadda). My ques

        • Even if you use small amplitudes or an almost ideal cantilever, the cantilever is still part of a bigger system with a thermal source (the outside, infinite degrees of freedom, yaddy yaddy yadda). My questions is not only considering thermal exchange, but also just the fact of leaking the wave fuction of the cantilever to "the outside".

          The note in Nature says they're going to keep everything very cold, which addresses this problem. Cooling can be viewed as "pumping away degrees of freedom", at least in

      • "Size doesn't matter."

        Women always say that. They lie.
      • The limiting factor will be inelastic flexion of the cantilever [...]

        Perhaps the limits could be expanded if you used a nanopulsed hyperinversion polarity tachyon field to reharmonize the chronometric particles?
  • Quantum mechanics research doesn't necessarily parle into bringing us closer to quantum computing! There is much heavy-lifting required in many, many areas...not just duality/entanglement and other popular areas.

    -psy
    • I still like using NMR and hydrogen spin states in common organic molecules to do quantum computing. The number of Q-bits is equal to the number of different hydrogens on a single molecule, and you can target each hydrogen with a separate magnetic pulse to manipulate that bit.

      Making a "macroscopic" object enter a quantum state is really cool, but I don't foresee it being a step directly towards quantum computing. (Though there may be spin-off learning).

      Of course, one would imagine that the wavefunction
  • Didn't Fenyman have experiments done with two holes in a divider between a photon emmiter and detector? Every attempt to measure which hole a photon went through on it's way to a detector collapsed the system such that the photon took only one path. No Interference.

    Sounds to me like nature has code to see if a debugger is attached to her processes, and if so, she ain't going to show you what she really does when you aren't looking.

  • It's amazing that people haven't figured this out already.

    If the rules state that you can not directly observe the cat, then you indirectly observe the cat.

    You observe byproducts or effects of the cat. Observing the things that the cat influences - be it live or dead will tell you the state of the cat.

    Sooo, in a stretch, it is possible to get closer to that which Shroedinger and Heisenberg stated were not possible.

    • If the rules state that you can not directly observe the cat, then you indirectly observe the cat.

      The distinction between "direct" and "indirect" observation is meaningless in this context. Observation is observation. Whenever ANYTHING requires the cat's waveform to collapse, it will collapse.

      • After a nice little New Scientist search, I see evidence that quantum states can be determined by observation of what they affect without influencing their state. Soooo, I just might be right in the case below.

        http://www.newscientist.com/news/news.jsp?id=ns 9 99 93384

        "Jian-Wei Pan and colleagues from Anton Zeilinger's group at the University of Vienna had already shown that, in theory, teleportation can be confirmed by monitoring the outcome of the interaction that teleports the qubit. If both photons are
        • They where saying you could infer that the quantum state had been teleported by observing the results system after the collapse of the quantum strait. This is not the same as being able to indirectly inferring the quantum state of the system without collapsing it (Schrodinger did not expect any difficulties in telling if the cat was alive once the box was opened). If we could not infer anything about quantum straits and could not measure them then I think it would be safe to say the do not exists. Interes

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