AMA | October 2024

9337.246 - 9362.086 Sean Carroll

It's just a change of basis. Indeed, it's just a rotation of the basis by 45 degrees. So spin plus x, I'm not going to get the signs right here, so forgive me, but roughly speaking, spin plus x is 1 over the square root of 2, spin up plus spin down in the z direction. Spin minus x is 1 over square root of 2, spin up minus spin down in the z direction. So they're just related to each other.