We know from classical mechanics that angular momentum [itex]L = r \times p[/itex] depends on your choice of origin. My question is: How does this work quantum mechanically? We know we get certain eigenvalues, but does this apply only in a certain choice of origin? How do we calculate angular momentum at some other point? I had a similar problem concerning torque on a magnetic dipole, [itex]\tau = \mu \times B = r \times F[/itex]. About what point do we measure the moment arm? Do we just assume our origin is at the "center" of the orbit? Thanks for the help.