Understanding Quantum Eraser Experiments

[bhobba]

I don't want to get into this fight, but I think that interpretations so far are just that

Indeed they are.

Well said.

Thanks
Bill

 

[alexepascual]

Indeed they are. Well said. Thanks
Bill

But when I said that they are just interpretations I did not mean to diminish their importance.
And even I know you will disagree on this, I consider the "ensenble interpretation" also as a "interpretation"
But I am not saying that you are wrong and I am right. I am just saying that we have different points of view.

 

[bhobba]

And even I know you will disagree on this, I consider the "ensenble interpretation" also as a "interpretation"
But I am not saying that you are wrong and I am right. I am just saying that we have different points of view.

The ensemble interpretation is just an interpretation like any other - it's what I hold to - but that means nothing.

No interpretation is better than another - they are all simply different viewpoints.

Thanks
Bill

 

[Gerinski]

In my humble opinion, an electron passing through the slits unobserved is like a qbit, it is both 0 and 1 simultaneously. An 'observation' is anything which turns that qbit into either a 0 or a 1 (= slit A or B). It doesn't matter what, when, where or who will 'notice' that change. A bit in the universe's information has been changed. The 'superposed' 0+1 was one state. A 0 is a different state, and a 1 is yet another different state. If we setup the apparatus so that it is not 'observed', the state will remain as it was, 0+1 simultaneously, we will not have caused a change in that bit of the universe's information. If we cause the qbit to change to either 0 or 1, (even if we do not 'look' at that change), that constitutes an 'observation'.

 

[Swamp Thing]

This wave particle stuff is wrong - here is the 'correct' explanation of the double slit:
http://arxiv.org/ftp/quant-ph/papers/0703/0703126.pdf

If I understand Marcella correctly, the slits prepare a state in terms of position, and the detection screen measures the momentum.

Would it be ok to say instead, that:
(a) The slits put the system in a certain position state, which is equivalent to the sum of many momentum states
(b) The system evolves in time from this initial state, such that the corresponding projection back onto the position basis also evolves in time
(c) The evolution thus takes the system through various states which are the sums of many position states
(c) Finally, the screen measures the position again at some point in its evolution.

Is this a valid, and mathematically equivalent, description to Marcella's? If so, then - although more complicated when described in words - it is perhaps a more acceptable picture. After all, a screen actually measures position and not momentum!

 

[bhobba]

Is this a valid, and mathematically equivalent, description to Marcella's?

Close enough.

For completeness I need to also mention while this is a more more satisfactory analysis of the double slit its still not quite correct:
http://arxiv.org/pdf/1009.2408v1.pdf

It's not as bad as the above makes out because these type of simplifying assumptions are made all the time in mathematical modelling. But it is an unfortunate characteristic of some areas in physics that as you proceed from beginning explanations you see what went before was wrong. In this case that would be the wave particle duality at the beginning level, to the intermediate one once you have learned the QM formalism (that would be the Marcella paper), to the advanced level (that would be the above).

Thanks
Bill