To get a distribution of some dynamic variable of a wavefunction, we actually need to prepare an ensemble of particles, in which all the particles have the same wavefunction, right? And no-cloning theorem states that it's impossible to copy an unknown quantum state. So is this a contradiction？ I've figured that in order to prepare an ensemble we have to know the wavefunction, so it doesn't really fit the situation under which the no-cloning theorem applies. But I can't really give myself a clear and detailed reasoning to convince myself. Could you guys help me explain it?