Quantum Mechanics: Measuring Position and Momentum

[bodensee9]

Homework Statement

Hi, Let's say that I measure the position of a system and I get that it is at X. So then if immediately after I measure the momentum, will I get:

1/sqrt(2*pi)* integral (exp(ikX))*(exp(-ikx))dx?
But this integral is undefined?
Then how do I find the momentum wave after measuring position? Thanks!

Or will my momentum just be exp(ikX)? for all range of K?

Thanks.

 

[arkajad]

That depends on how you measure the position - with which device and with which accuracy. In cloud chambers positions are being measured again and again, many times on the same particle, and nothing dramatic happens to the momentum.

 

[vela]

Are you asking about actually measuring the momentum immediately after you measured the position of the system, or are you just trying to find the momentum-space representation of the state after the measurement?