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## Summary:

- What happens to the uncertainty principle if we could build this experiment

## Main Question or Discussion Point

I just read the Feynman Lectures about the electron gun experiment with two holes in the middle wall.

It demonstrates that if we don't look at the electrons while they travel toward the detector there is an interference pattern in the probability curve of the electrons similarly to what happens with waves. But if we try to measure which hole the electron passes through the probability pattern changes and the electrons behave like bullets.

At the end of the lecture there is a further experiment this time with a wall with rollers --> here <--

I don't understand much the details of the latter experiment but it turns out that even in this situation is not possible to break the uncertainty principle.

My question is what would happen in the following situation:

We have the middle wall but this time the two holes are replaced with two detectors that perform the following actions:

- retrieve all the information about the electron speed, angle/direction, spin, hole A or B, etc...

- block the electron

- shoot another electron or the same electron with the same speed, angle/direction, spin etc... that has been retrieved before it was stopped.

This way the new electron has the same properties that would have had the original electron if it was not watched by the machines and it goes on toward the backstop with the movable detector described in the lecture.

What is the probability curve of such situation? Will it have interference or not?

It demonstrates that if we don't look at the electrons while they travel toward the detector there is an interference pattern in the probability curve of the electrons similarly to what happens with waves. But if we try to measure which hole the electron passes through the probability pattern changes and the electrons behave like bullets.

At the end of the lecture there is a further experiment this time with a wall with rollers --> here <--

I don't understand much the details of the latter experiment but it turns out that even in this situation is not possible to break the uncertainty principle.

My question is what would happen in the following situation:

We have the middle wall but this time the two holes are replaced with two detectors that perform the following actions:

- retrieve all the information about the electron speed, angle/direction, spin, hole A or B, etc...

- block the electron

- shoot another electron or the same electron with the same speed, angle/direction, spin etc... that has been retrieved before it was stopped.

This way the new electron has the same properties that would have had the original electron if it was not watched by the machines and it goes on toward the backstop with the movable detector described in the lecture.

What is the probability curve of such situation? Will it have interference or not?