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Physics, Astronomy & Cosmology / Trying to understand Quantum Entanglement
« on: 03/11/2010 12:44:37 »
I have been trying to understand why Quantum Entanglement is so spooky, I do not see the problem.
If we pass a photon through a polariser then it will emerge with a certain polarisation, which is defined by an angle. The photon 'knows' what its polarisation is, because if it meets a second polariser at 90 degrees to the first it is certain to be absorbed, so the state is well-defined. However, someone who doesn't know that the photon has been through a polariser cannot determine the polarisation, all he can do is pass it through a filter and see what happens, but this does not tell him exactly what the polarisation was.
So a photon can have a well defined polarisation, but we cannot determine exactly what it is.
Now why can't entangled photons also have this same well defined but indeterminate polarisations when they are produced? Doesn't this remove the problem of superluminal communication? Why is this explanation incompatible with quantum theory?
If we pass a photon through a polariser then it will emerge with a certain polarisation, which is defined by an angle. The photon 'knows' what its polarisation is, because if it meets a second polariser at 90 degrees to the first it is certain to be absorbed, so the state is well-defined. However, someone who doesn't know that the photon has been through a polariser cannot determine the polarisation, all he can do is pass it through a filter and see what happens, but this does not tell him exactly what the polarisation was.
So a photon can have a well defined polarisation, but we cannot determine exactly what it is.
Now why can't entangled photons also have this same well defined but indeterminate polarisations when they are produced? Doesn't this remove the problem of superluminal communication? Why is this explanation incompatible with quantum theory?