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Is the wave function a relative wave (entanglement)

  1. Aug 19, 2012 #1
    Is the wave function a "relative" wave (entanglement)

    Alice and Bob build a quantum entanglement experiment with the help of a lab technician.

    The experiment runs and a quantum entangled pair is created but unbeknown to Alice & Bob the technician puts his own measuring device in the experiment and takes a measurement before Alice & Bob get a chance to do their measurement.

    When Alice & Bob make their measurements they are confronted with the same uncertainties , Alice makes a measurement and assumes the wave collapses but the assistant had already collapsed the wave.

    With that said is the collapse of the wave relative to the observer?
  2. jcsd
  3. Aug 20, 2012 #2
    Re: Is the wave function a "relative" wave (entanglement)

    Alice and Bob, in this case, won't get the correlated (same/opposite) measurement.

    If Alice shows 1/up, Bob won't necessarily show 0/down because time has passed since the lab technician made his measurement. The two photons' states start to evolve separately after the technician's measurement.
  4. Aug 20, 2012 #3
    Re: Is the wave function a "relative" wave (entanglement)

    Thanks for the explanation, I had no idea that the entangled properties were disentangled after a measurement is taken. I see now why it can be used to determine if private message has been read by somebody else :smile:
  5. Aug 20, 2012 #4
    Re: Is the wave function a "relative" wave (entanglement)

    This now raises another question, if both particles are measured at exactly the same time and then say a thousandth of a second later the same measurements are repeated will they still be entangled?
  6. Aug 20, 2012 #5
    Re: Is the wave function a "relative" wave (entanglement)

    No. You should focus on the uncertainty principle(a cornerstone of qm) and why it was immediately clear to the founders of qm why entanglement of position/momentum would ensue between interacting particles(later confirmed in experiments). Entanglement is basically a confirmation of the Uncertainty principle over all of spacetime and across all frames of reference(i.e. in that sense, it's not relative to the observer and appears to happen instantaneously as far as current experiments can reveal).
    Last edited: Aug 20, 2012
  7. Aug 20, 2012 #6
    Re: Is the wave function a "relative" wave (entanglement)

    Thanks for the confirmation on loss of entanglement after the first measurement, I must say that when seen on TV this seems to be a fact that I have never heard. I've often wondered what was so special about the claims of entanglement and its not until you realise that the property is broken when measured that it becomes "odd".

    If you could entangle three particles at once you could communicate instantly over any distance by sending two streams to a receiver and keeping one stream of particles for yourself. if after say one year the two streams reached the recipients you could measure particles in your stream and the discrepancies at their end would contain the message. With that said its probably impossible otherwise it violates speed c.
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