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Understanding spin and axis in quantum entanglement

  1. Nov 15, 2012 #1
    I don't have a good grasp of "spin along axis" topic, so pardon my dumb questions:

    1. Does a photon/electron have a different spin across each of the 3 axis?

    i understand that the spin of an electron/photon is not the same as that of, say, a ball

    2. Gravity can distort time-space (and hence the axis?).

    Alice is in a gravity free part of space-time. Bob takes the other entangled photon and is in a space-time region that is distorted by gravity.

    If Alice measures the spin of her entangled photon along say the "x-axis"

    how does Bob figure out what his "x-axis" is? does Bob simply make adjustments for the new Cartesian system based on the formulas (for distortion of space time by gravity)?

    3. If a photon is travelling along x-axis, does it have one spin each for each of the three axis? thus a total of 3 spins....if you are making calculations in the Cartesian system
    Last edited: Nov 15, 2012
  2. jcsd
  3. Nov 15, 2012 #2


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    Good question. Bob's particle must be noninteracting until it is measured. In a curved spacetime this means the particle follows a geodesic, and its spin axis is parallel transported. So although each of Bob's axes x, y, z may not be "the same" as Alice's, they correspond uniquely to those of Alice.
  4. Nov 15, 2012 #3
    well answered, thanks Bill
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