Hi, Assume we have a source that emits several copies of the same quantum state which is a superposition of several eigenstates of the Hamilton operator with different energies. We can calculate the expectation value of the energy of this state and therefore also the energy the source releases, which is the same for each state. However, if we measure the energy, the system collapses to one eigenstate with a specific energy. How does this comply with conservation of energy? I guess there must be some energy exchanged with the measurement device, but in standard quantum mechanics there is no framework for the measurement process itself that could explain this exchange.