In the reality how I perform the many kind of measurements, like operators p,q,E

[spocchio]

in the experimental side of QM, I know i can use a slit to measure the q.
but what about p or E?

and how to conciliate the measure with the theory?:
after the measurement of a slit i'll measure q and the system will collapse in a autovector of q, like |q>
but it will evolve like a dirac-delta in <q| ! and where the information of the size of the slit comes?
have I to consider a non-selective measurement in q?

 

[The_Duck]

To measure the momentum of a charged particle you can send it through a magnetic field. The more momentum it has the larger the radius of curvature of its trajectory will be. Then measure its position; this now tells you its trajectory and thus its momentum. If you know the mass of the particle you can use its momentum to calculate its energy.