Density Matrix of Unpolarized Light

[annaphys]

Homework Statement

Attached 31.i and ii

Relevant Equations

Attached

I have unfortunately no attempt for 31.i. I don't know how to start the problem. 31.ii is attached. Can someone give me a tip on how to start 31.i? I also have troubles solving 29.iii. I have attached that as well.

 

[DrClaude]

When you have a purely statistical mixture, the density matrix contains the probabilities of the different outcomes on the diagonal and zeros everywhere else.