I know the following question is elementary, but being a dilettante in QM, I am confused on the following. So, I have two questions. The first question is whether the following reasoning is correct, and if not, why not. First, the Heisenberg Uncertainty Principle (HUP) applies to Hermitian operators. Second, operators on spins are unitary. Thirdly, although Hermitian and unitary operators are not identical, there is a one-to-one relation given by the fact that for every unitary operator U there exists a Hermitian operator K such that U= exp(iK). Therefore there should be an equivalent to the HUP that one can apply to the unitary operators which are used to go from one spin state to another, for example on the Bloch sphere. The second question is: if the above is correct, then what is this equivalent principle? If it is not, is there any way that the HUP is used on operators on spin states? Hope the question does not appear too stupid; thanks in advance for the answers.