Exploring Quantum Mechanics: Interference Experiments with Entangled Particles

[feizex]

Hi,

This is my first post here. I have done some reading on quantum mechanics and am curious to know more.

I know about the double slit experiment and the interference pattern produced. I have also read of entangled pairs.

My main question is:

If you have a pair of entangled particles (say an emitted photon pair, or electron pair?) and you attempt an interference experiment on one of the entangled particles, can you still perform an interference experiment with the other?

If not and the wavefunction collapses or decoheres(?) presumably the apparatus that was closest to the source will show the interference and the one further away will not?

What happens if they are both at the same distance?

As an aside, I have also read that the quantum "wavelength" for a grain of sand is shorter than it's physical diameter so you can't perform an interference experiment with it. Is that true? Doesn't that imply that anything larger than a grain of sand has a known location?

Thanks!

 

[Demystifier]

If you have a pair of entangled particles (say an emitted photon pair, or electron pair?) and you attempt an interference experiment on one of the entangled particles, can you still perform an interference experiment with the other?

No, you cannot. (This is also related to the delayed choice experiments, in which interference can only be seen as encoded in the coincidences between the entangled pairs.)

If not and the wavefunction collapses or decoheres(?) presumably the apparatus that was closest to the source will show the interference and the one further away will not?

No, neither of them will show interference. Interference can only be seen through coincidences.

What happens if they are both at the same distance?

It will not change anything.

As an aside, I have also read that the quantum "wavelength" for a grain of sand is shorter than it's physical diameter so you can't perform an interference experiment with it. Is that true? Doesn't that imply that anything larger than a grain of sand has a known location?

That is true in practice, but not in principle. In principle, even a grain of sand could show interference.
In practice, physicists can do interference with atoms and molecules, the size of which is also much bigger than their wavelength.