- #1
astrofunk21
- 29
- 0
Hey all!
I am prepping myself for a quantum course next semester at the graduate level. I am currently reading through the Cohen-Tannoudji Quantum Mechanics textbook. I have reached a section on the density operator and am confused about the general concept of the operator.
My confusion stems from the question, why can't we continue to state vectors to describe a system all the time. The textbook says that it leads to clumsy calculations if we apply weighting (pk) to a certain state (|ψk>) and sum over k.
In the pure case we can use both the density operator or state vector to describe the system. Yet with a mixed state we cannot. Where do these two methods diverge and the state vector method fails?
Maybe I am being blind, but this concept has seemed to stump me so far. Would appreciate a qualitative explanation to maybe sort this out.
I appreciate any help you guys give!
Textbook image: https://ibb.co/di6MO6
I am prepping myself for a quantum course next semester at the graduate level. I am currently reading through the Cohen-Tannoudji Quantum Mechanics textbook. I have reached a section on the density operator and am confused about the general concept of the operator.
My confusion stems from the question, why can't we continue to state vectors to describe a system all the time. The textbook says that it leads to clumsy calculations if we apply weighting (pk) to a certain state (|ψk>) and sum over k.
In the pure case we can use both the density operator or state vector to describe the system. Yet with a mixed state we cannot. Where do these two methods diverge and the state vector method fails?
Maybe I am being blind, but this concept has seemed to stump me so far. Would appreciate a qualitative explanation to maybe sort this out.
I appreciate any help you guys give!
Textbook image: https://ibb.co/di6MO6