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Quantum Measurements Leave Schrödinger's Cat Alive 210

Posted by samzenpus
from the looking-in-the-box dept.
First time accepted submitter Walking The Walk writes "Your co-workers who keep using Schrödinger's cat metaphor may need to find a new one. New Scientist reports that 'by making constant but weak measurements of a quantum system, physicists have managed to probe a delicate quantum state without destroying it – the equivalent of taking a peek at Schrodinger's metaphorical cat without killing it. The result should make it easier to handle systems such as quantum computers that exploit the exotic properties of the quantum world.'"
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Quantum Measurements Leave Schrödinger's Cat Alive

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  • by Sun (104778) <shachar@shemesh.biz> on Thursday October 04, 2012 @12:41AM (#41545815) Homepage

    This wouldn't allow you to gain a "strong" piece of information – whether the cat was alive or dead – but you might be able to detect other properties.

    So, in essence, the main thing they found out is how to do more stuff with qbits without triggering a collapse of the wavelength function.

    Real summary:
    Obscure need which is somehow quantum computing, but not in any way feline, related gets obscure advance.

    Shachar

  • by Anonymous Coward on Thursday October 04, 2012 @12:46AM (#41545837)

    This is the equivalent of weighing the box. By not opening the box you don't collapse the wave function. Instead you measure some other property that is independent of the wave function. It is nothing like peeking in the box, nor does it gain any information from the wave function.

  • by Yvanhoe (564877) on Thursday October 04, 2012 @01:30AM (#41546003) Journal
    I thought at this point is had become obvious that quantum cryptography was just a nice scam to fund fundamental physics research?
  • New Scientist? (Score:5, Informative)

    by edibobb (113989) on Thursday October 04, 2012 @01:34AM (#41546019) Homepage
    The New Scientist frequently makes quantum leaps in logic. Or was that logic leaps in quantum physics? I GET SO CONFUSED! At any rate, the real article is a bit less sensational.

    http://www.nature.com/nature/journal/v490/n7418/full/nature11505.html [nature.com]
  • Re:first post ! (Score:5, Informative)

    by Anonymous Coward on Thursday October 04, 2012 @03:20AM (#41546369)

    Does anyone here RTFA?

    Yes, I did. The summary quotes this part line by line: "physicists have managed to probe a delicate quantum state without destroying it – the equivalent of taking a peek at Schrodinger's metaphorical cat without killing it."

    This shows a fundamental misunderstanding of the cat experiment, in that the author is assuming that by opening the box the cat gets killed. When in fact the cat can be considered both alive AND dead while the box is unopened, and if you open it it might very well be alive and not dead. Thus it would be equally accurate (or inaccurate, rather) to say "the equivalent of taking a peek at Schrodinger's metaphorical cat without making it LIVE."

    And to be even more nitpicky, it does alter the quantum state- it changes the oscillation but does not destroy the superposition. They also have (simply put) found a way to return the oscillation to the pre-observation state within a relatively small timeframe.
    So yes, the parent's "???" was justified as the use of the analogy was horrible incorrect.

  • by Guignol (159087) on Thursday October 04, 2012 @05:12AM (#41546747)
    If the cat was just either dead or alive (according to whether or not the gun, or poison or whatever was triggered by some beta decay) and we would just be unaware of it until opening the box
    What would be wrong about it ?
    You put a coin in a box, shake the box. surely, it is either head or tails, you just know what it is when you open the box
    So why do you think there is such a buzz around the Schrödinger’s cat ?
    Precisely because, the experiment is setup so that the cat is not either alive or dead, but in a special state
    Schrödinger put together this thought experiment to show how silly the Copenhagen interpretation was (to his eyes)
    The experiment is there to say "according to you, the cat is both dead and alive (which we can all agree on is ridiculous)"
    Except it's not that simple, and then, there is entanglement and there indeed are "weird mixed states"
  • "One atom per hour" (Score:4, Informative)

    by Kupfernigk (1190345) on Thursday October 04, 2012 @06:55AM (#41547137)
    No, that too is incorrect. Radioactive decay is random. With a very slow rate of decay ( averaging one event per hour) the time between events will, I think, follow a Poisson distribution. The probability that the cat is dead does indeed increase with time, but it is not 1 at 1 hour, or even 2.

    My dog suggests that this should be tested with a very large number of cats, and a big lump of polonium in each box.

  • by ceoyoyo (59147) on Thursday October 04, 2012 @08:09AM (#41547441)

    No, you don't get to peek at the cat's state. You can peek at some other property, like how fast it's transitioning between (quantum) states, but you can't see the cat's state.

    To use the analogy of the thought experiment, maybe you could peek in the box and determine whether there is a cat in the box at all, or what colour it is, but if you look long enough to determine whether the cat is alive or dead then you'll destroy the superposition.

I tell them to turn to the study of mathematics, for it is only there that they might escape the lusts of the flesh. -- Thomas Mann, "The Magic Mountain"

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