# Homework Help: Repeated Measurements

1. Oct 30, 2008

### daveyman

1. The problem statement, all variables and given/known data
This is a true or false question on a practice test. I'm having a hard time making sense of it. Here it is:

Two operators A and B do not share eigen states a(n) and b(n) where n=1,2,3,etc. A measurement of A is made and the system is found to be in state a(1). If the measurement of A is repeated at some later time, and if A does not commute the Hamiltonian H, the system may be found to be in a state other than a(1) (True or False).

2. Relevant equations
N/A

3. The attempt at a solution
My guess is true, but I'm not sure how the phrase about the Hamiltonian plays into this.

2. Oct 30, 2008

### olgranpappy

The hamiltonian play a role because it determines how the state changes with time.

3. Oct 30, 2008

### daveyman

So, since the two operators do not commute, that means the state is changing with time, correct? This definitely means the answer is true.

Please correct me if I am wrong - thanks!

Last edited: Oct 30, 2008