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A 'Classical' object behaving Quantum?

  1. Dec 1, 2011 #1
  2. jcsd
  3. Dec 1, 2011 #2
  4. Dec 1, 2011 #3
    What is the original article entitled? In which journal was it published? I might be able to access it via a database my university subscribes to, but it may be a while until I can access it. Usually there is embargo on new articles for a month.
  5. Dec 1, 2011 #4
    It is usually easy to find articles by searching on the authors. In this case the name is unusual so it should be very easy. I didn't find anything, so perhaps it is not yet online.

    As best as I can tell, in my VERY inexpert opinion, the situation is this:

    Two diamonds. Input a light pulse that is capable of creating a phonon -- a quantum of sound energy -- in a diamond. Split the pulse into two entangled pulses and direct these into two diamonds. If the pulse lost energy then the phonon has been created. The question is, is the phonon in one diamond or are both diamonds entangled, with the phonon in no specific one? That is, is each diamond in a superposed phonon/no phonon state?

    Another pulse is sent in to destroy the phonon, it's energy going into the pulse. Like the first pulse, the pulse is split into two entangled pulses, one for each diamond, sent through the diamonds, and recombined. If the diamond/phonon systems are not entangled, then only one of the pulses will get the energy. It's wavelength will shorten, and it will then interfere with the other half of the pulse. If the systems are entangled and in superposed states, then the two pulses will have the same wavelength and not interfere. The latter was observed.
  6. Dec 1, 2011 #5
    It was published in Science, Dec 2.
  7. Dec 1, 2011 #6
    Nothing came up when I did a search on Web of Knowledge, for the titles given on this page: http://www.sciencemag.org/content/334/6060/1253.abstract
  8. Dec 2, 2011 #7

    A. Neumaier

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    There is a big difference between the grandiose claim of entangled diamonds and what they really did, if you read the fine print: The achievement in the main text simply reads
    ''the diamonds shared one vibrational state between them''

    So they entangled vibrational states, not diamonds.

    Claiming they entangled diamonds is like claiming glass fibers to be entangle just because they contain a pair of entangled photons. This is nothing new but a very old hat. new is only the exaggeration.
  9. Dec 2, 2011 #8
    We are in agreement on this one, maybe from a different perspective. Let's do some back-of-the-envelope calculations:
    1 fs (femtosecond) = 10-15s. Laser pulse duration = 100 fs Time between laser pulses = 350 fs. Speed of sound in diamond v ~ 12000 m/s. From this one easily can estimate how far a phonon can spread/propagate in 350 fs as dx = v*dt = 12000*350*10-15 = 4.2*10-8m = 4.2*10-5mm. Given the diamonds were each around 3mm in size, then if roughly cubic in shape, the fractional volume occupied by phonon at end of dual pulse run is of the order 4*pi/3*(4.2*10-5/3)3 ~ 10-14. So to say 'the diamonds' were in a state of superposition does indeed seem just a trifle exaggerated! The above assumes a classical spherical spreading pulse as 'phonon', but that is therefore probably a somewhat overestimate of volume occupied by excited material.
    Last edited: Dec 2, 2011
  10. Dec 2, 2011 #9
    All you can really do is entangle the physical properties of the diamond, in this case the physical property of the crystal, the vibrational state, was.

    I don't think the comparison is warranted. Photons aren't physical properties of glass fibre.
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