- #1
Silviu
- 624
- 11
Hello! I got a bit confused about the fact that the whole the description of spin (and angular momentum) is done in the z direction. So, if we are told that a system of 2 particles is in a singlet state i.e. $$\frac{\uparrow \downarrow -\downarrow \uparrow }{2}$$ does this mean that measuring the spin of the first one on ##\textbf{any}## axis (not only z) will ensure that measuring the spin of the second one will give the opposite result? Or is this form true only for the z axis, and if we want to check on other axis, we need to project the up and down of the z axis onto the orthonormal basis of this other system of axis and work from there? Thank you!