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Quantum entanglement and Two slit experiment

  1. Jul 8, 2011 #1

    Firstly, I'm not a physics student but was just wanting some answers to questions from those that are, so I thought I'd try you lot. :smile:

    1. Has anyone proved that quantum entanglement doesn't happen at the macro level?

    2. Regarding the 2 slit experiment and how consciousness collapses a wave to particle, has anyone proved that it doesn't happen on a macro level?

    Layman's language would be much appreciated :wink:

    Thanks very much.
  2. jcsd
  3. Jul 8, 2011 #2


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    Welcome to PhysicsForums, itsonelouder!

    1. It is generally believed that any entanglement of macro objects will self-decohere (ending the entanglement) in relatively short time spans. The system more or less needs to be closed to maintain the entangled state. That does not mean that it is impossible, and some experimentalists are working on accomplishing this.

    2. I don't know of any way to prove or disprove that consciousness causes wavefunction collapse. However, it is generally not believed to be a factor.
  4. Jul 8, 2011 #3
    And definetely not if you have a professionnal training in the field of neurosciences and cognitive psychology.
    Only a totally ignorant in neurosciences could believe that the heart of microphysics could have anything to do with the neuronal machinery of consciousness.

    However, for the social psychologist who is interested in rumors and collective deliria, the history and development of this believing is an interesting and rich corpus.
    Last edited: Jul 8, 2011
  5. Jul 8, 2011 #4

    1. So it hasn't been disproved, it isn't out of the realm of possibility. Isn't the universe a closed system though? All matter coming from the quantum field, and the matter is the same as the field? One field of energy, therefore a closed system?

    To quote Einstein: We may therefore regard matter as being constituted by the regions of space in which the field is extremely intense...There is no place in this new kind of physics for the field and matter, for the field is the only reality."

    2. I thought that conscious observation was believed to be the influencing factor, because as soon as conscious observation occurs the wavefunction collapses? So has no scientist proved this phenomena can't occur with everyday objects?

    Sorry if I'm repeating myself.
  6. Jul 8, 2011 #5
    So if consciousness isn't causing it, what is? And has it been proven conclusively that consciousness doesn't collapse the wavefunction?
    Last edited: Jul 8, 2011
  7. Jul 8, 2011 #6
    Lots of things can "observe" a wavefunction. Any kind of sensor or particle that interacts can collapse its wavefunction.

    Has it been proven conclusively that consciousness doesn't collapse the wavefunction? No, it hasn't.

    Now answer me this, has it been proven conclusively that the universe isn't actually riding on the back of a giant tortoise made of jello and paper clips by deranged monkeys strung out on crack and diet pepsi?
  8. Jul 8, 2011 #7
    But there's nothing to suggest your last hypothesis. Yet, doesn't experimental evidence repeatedly show the collapse of the wavefunction when it's consciously observed?
  9. Jul 8, 2011 #8
    Not at all. If you put photon detectors in each of the slits that click when a photon passes them you destroy the interference pattern even if you aren't in the room listening to the click.

    So, either photon counters are conscious, or there is no evidence consciousness is needed to collapse wavefunctions.

    Wavefunctions collapse when they are "observed" by anything... people, machines, other particles...
  10. Jul 8, 2011 #9


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    There is no reason to suppose that consciousness is a factor, no. It would be like saying that light travels at c only when we measure it. There is no hypothetical mechanism for a role for the mind.
  11. Jul 8, 2011 #10
    Thanks. How does another particle observe a photon? Does that mean photons behave as a wave in a vacuum, but a particle in non-vacuum. And how do you know it's a wave when it's not being observed? That sounds impossible.
  12. Jul 8, 2011 #11
    A particle observes a photon by interacting with it. For example, it is partially scattered by the interaction. And for two particles to interact, they need a definite position.

    I think you are missing the point of quantum mechanics. A photon is not a wave sometimes, and a particle at other times. It possesses both particle-like and wave-like qualities. This is the so-called Copenhagen Interpretation favored by Niels Bohr. Richard Feynman thought photons are particles that have some wave-like "quantum weirdness" nature. So while there is some room for debate, I don't believe anyone really believes photons behave as a wave in a vacuum, but a particle in non-vacuum.

    How do we know photons have wave-like nature? Because that theory leads to predictions that can be tested by experiment, and these experimental results match theory to an astounding accuracy. That is really, really strong evidence that quantum mechanics is either a deep truth of nature or an accurate aspect of some deeper truth.
  13. Jul 8, 2011 #12
    It's absolutely fascinating stuff, so I'm going to go away and read up some more and maybe get back to you. I'm not sure about this observer thing and what constitutes an observer.

    Thanks very much so far :smile:
  14. Jul 8, 2011 #13
    Quick question. You mentioned that interaction with particles constitutes an observer. But when the photon behaves like a wave when passing through the two slits, isn't it interfering with the particles in the material the slits are made of? And what about the air particles?
  15. Jul 8, 2011 #14
    The idea that particles must collapse each other's wave functions if they interact conflicts with my understanding of quantum mechanics. I thought that you could instead construct the wavefunction of the two-particle system, and this wavefunction would not collapse when the two particles interact.
  16. Jul 9, 2011 #15
    Consciousness, consciousness, consciousness...

    Using so heavily a technical and specialized word implicitly asserts that you understand and master it.
    If so, please do not hesitate to give us a scientific definition, which has a practical use.
    Please remember us the exact role of the raphé.
    Please remember us the exact role of the locus coeruleus.
    Please remember us the exact roles of the hippocampi and the amygdalia.
    Antonio Damasio has also given us several names of nuclei in the cerebral stem, which are not in my neuro-anatomy atlas, and all play a crucial role in consciousness. Please explain them.
    Please explain the roles of parietal associative areas in self-consciousness of our own body.
    We begin to know them by cerebral accidents - mainly vascular ones.

    From the evolutionary point of view, please explain when began the "consciousness" used by the Copenhagen fairy tales. Before or after mastering the fire ? Before or after elaborating wood tools then stone tools ? Before or afer the separation of primates from rodents ?
    Please explain us how the planets and stars could achieve their nuclear and chemical reactions, looooooooooong before Copenhagen physicists began to suck their mothers, then observe quantum reactions.
    Thank you !
    Last edited: Jul 9, 2011
  17. Jul 9, 2011 #16
    Re: Consciousness, consciousness, consciousness...

    Has it been proved that consciousness is a function of the brain? Many forms of life display consciousness of their surroundings and they don't have a brain. Or is it just a by-product of life?

    There would have to be consciousness of your surroundings before all of what you say. Without consciousness you wouldn't be conscious of anything and so you wouldn't be able to do anything. ;-)

    Well obviously stuff was happening before life. What was causing that i don't think anyone knows do they? But there's some natural force/order/beauty to the universe. Look at the fractal geometry in nature. I never said consciousness has to exist for stuff to happen.
  18. Jul 9, 2011 #17
    This may seem a silly question, but in the case of the above, has it been proven that the wavefunction collapsed "before" you observed it's collapse.
  19. Jul 9, 2011 #18
    Re: Consciousness, consciousness, consciousness...

    Have you heard the of term "Separation Conscious" yet?

    It's the idea that consciousness is a distinct separate thing from both the mind and body, meaning that we are aware of our five senses, through which we also perceive biochemical reactions that we call emotions, just as we are aware of our thoughts, which can cause the limbic system of the brains to stimulate the autonomic nervous system, which also affects the body producing biochemical reasons that we again we interpret as emotion. This is just the same as saying that the sight of an attractive woman can make a man amorous or the thoughts of having been robbed can make one angry.

    The point is we are aware of our feelings and thoughts, although those things are distinctly separate from our awareness of them. So is the brain the source of consciousness? I have to say the brain, as we commonly think of it as the organ that allows us to reason and remember, is a kind of computer at the disposal of the consciousness. I also tend to think the solar plexus may more likely be the attachment point between the conscious and the mind/body dichotomy, although at the moment I lack a proof of it.
  20. Jul 9, 2011 #19
    Re: Consciousness, consciousness, consciousness...

    I've done some meditation in my time and I know that it's possible to be conscious of your thoughts as opposed to feeling you are the thoughts. In other words, observing the trance-like state of conditioned thought processes and seeing them as not self. But I get the feeling there is no dualism there, everything being a manifestation of the same substance.
  21. Jul 9, 2011 #20
    Yes, absence of dualism. The power of thought to draw the consciousness in is quite strong. That's why some many people identify with their thought. It's easy to do.

    By quieting the mind and relaxing as much as possible, one can begin to become aware of just being aware and amplify upon that. "The Power of Now" was an incredible help to me along those lines.

    I had meditated for decades before reading that with varying levels of success. Although after reading that book, zoom, up to a whole new level. I also use binaural beats quite a lot, although those actually remap activity in certain part of the brain.
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