Nielsen & Chuang list three axioms for QM. I paraphrase them as follows: 1. States are unit vectors. 2. The evolution of a state is unitary and given by the Schrodinger equation. 3. The measurement of a state yields a value from a probability distribution. The state just before the measurement may be different than just after and also random. So 2. says the evolution is deterministic and 3. says it's stochastic. I've seen many treads that dance around this issue, but no clear resolution. Seeking enlightenment.