Chinese Satellite Achieves Quantum Entanglement Distance Record

Discussion in 'Physics & Math' started by danshawen, Jun 16, 2017.

  1. arfa brane call me arf Valued Senior Member

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    . . . and the 9th or so paragraph starts with this:
    "Later the three get together to compare notes. Alice's and Bob's measurements were made at the same time, to within about 0.35 nanoseconds . . ."

    What's the significance of "Later", "compare", and "measurements"? That 0.35 nanosecond figure, what's the significance of that; where did they get it from?

    If you add in IBM's statement: "there is no action, but rather correlation", where does that leave instant telecommunication, when Alice and Bob actually compare their measurements later?
     
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  3. Write4U Valued Senior Member

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    I just ran across this ;
    Because @ "c" time stands still?
    http://zidbits.com/2011/05/why-cant-anything-go-faster-than-the-speed-of-light/

    Does this not suggest that from from the perspective of the entangled pairs moving @ "c", the spin reversal of one takes exactly zero seconds to cause the reversal of the other?

    This "relative to the observer" stuff at "c" causes some really interesting perspectives. It literally boggles the mind.
     
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  5. arfa brane call me arf Valued Senior Member

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    danshawen's link starts with:

    "Quantum entanglement, one of the odder aspects of quantum theory, links the properties of particles even when they are separated by large distances."

    This 'linking of properties' is something which is true because the particles weren't separated by large distances, they interacted 'locally' at some time, t.
    This 'moment of interaction' cannot be the same absolute time for all quantum particles.

    The article makes, and continues to make, assumptions about what entanglement is. It clings to this notion of "action at a distance", but the only action in the experiment is measurement, and the correlations are because of comparisons of measurements . . .
     
    Last edited: Jun 17, 2017
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  7. Write4U Valued Senior Member

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    I think I understand what you are saying, but if from the paticle's perspective time stands still, distance loses its meaning and they both exist in a permanent "local" state of t = 0
     
  8. Write4U Valued Senior Member

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    As I qualified before, I am out of my depth here. But as Antonsen demonstrated, if we can form a parabola from a set of purely straight lines, what else is possible?
     
  9. Nacho Registered Senior Member

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    LOL! Well, you did find the phrase "speed of entanglement". I'll give you that!

    Then it must be true, musn't it.

    Please Register or Log in to view the hidden image!

    But still, I think I'll wait for a consensus from more scientists.
     
  10. danshawen Valued Senior Member

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    Probably wise. I'm just impatient, that's all.
     
  11. danshawen Valued Senior Member

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    I'm not saying that everything 'moment of interaction' happens all at once for all quantum particles; only that there is a common, absolute instant (not an interval) of time involved with pairwise entanglement state changes whereever they occur, and that these are pairwise instantaneous.

    All of the particles of the universe are not entangled with each other, but the quantum field in which they are immersed is entangled everywhere at once.
     
  12. danshawen Valued Senior Member

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    Only if you go with Minkowski and divide by zero. Time and space are simply not related in that way. Too much is easily explained by treating time as real and space as an artifact. Conservation of mass/energy, for instance. Spooky action at a distance for another.

    The speed of light is not the basis of time. No velocity, invariant or otherwise, is the basis of time. To find what is the basis of time, what you are looking for is the fastest "slowest" process in the universe. If that is entanglement, is it really necessary to point out that you have found the basis of time? The propagation of light is a process, and that process itself takes time.
     
    Last edited: Jun 17, 2017
  13. arfa brane call me arf Valued Senior Member

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    Something that might make you think about that a bit harder:



    (from John Preskill, you may know who that is, the entanglement discussion starts with EPR at about 54 minutes).
     
  14. danshawen Valued Senior Member

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    If the quantum field in which qubits are created were not entangled everywhere, it would be impossible to store entangled information. Every electron in atomic structure in the entire universe is identical because of this. The lecture doesn't really suggest that it works any differently than I thought.

    Thanks. I need to view an update on quantum error correction. Error correction was an area of expertise that previously was my specialty.
     
  15. DaveC426913 Valued Senior Member

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    A critical aspect of relativity is that the speed of light is not a valid reference frame. It is nonsensical to imagine what might happen from a photon's point of view.

    Here's a demonstration:
    A frame of reference is - by definition - one in which the observer is stationary. That is what defines a frame of reference.
    A photon, by definition, always moves at the speed of light relative to the observer. It cannot do otherwise.
    To imagine from the perspective of a photon, one must posit a reference frame where the photon is simultaneously stationary AND moving at c with respect to itself.
    This is a paradox. It is not valid.


    As for quantum entanglement, while it indicates spooky action at a distance, it does not imply any ability to communicate as faster than light speed. I would be surprised if anything in the article suggested there were possibilities for faster than light communication.
     
  16. exchemist Valued Senior Member

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    Yup I knew that of course. I was interested in Dan's explanation of what it means in this context.
    Yes of course but I was interested to know
    Ah OK a pair of photons with opposite spin. Seems to me to be stretching the meaning to speak of a singlet state of something that can't lead to a spectral line, but if that's now accepted usage, then fair enough.
     
    Last edited: Jun 17, 2017
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  17. danshawen Valued Senior Member

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    That surprised me too, after Write4U mentioned it, but it does make sense. Evidently it doesn't require a lot of technology to make that entangled state happen with photons.
     
  18. arfa brane call me arf Valued Senior Member

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    So, since it is possible to store entangled information, and this in the context of quantum computing is a gate operation, the field is entangled "everywhere", even though we can only get entanglement information from those particles we know are entangled?

    Or, in other words, your theory appears to add something which isn't actually defined, it looks like an uneccessary hypothesis.

    You could say the gate operation that stores a classical bit in a classical computer is able to store the bit because of some quantum field that can't be measured. A null hypothesis.
     
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  19. danshawen Valued Senior Member

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    A qubit only has meaning if a qubit exists that has either has no meaning, or a simple meaning that is capable of being redefined by means of a quantum gate.in the same way that any non-quantum computer must have all of its registers initialized to put it into a known state, even if that state need not be observed once initialized.
     

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