5 Quantum dynamics
5.1 Unitary evolution
During a measurement, information is extracted from a quantum system, and in this process the state changes, either via the projection rule or not. But the state of a quantum system may also change over time even when the system is not being measured, when it is informationally isolated. Understanding this time evolution means understanding the dynamical laws governing quantum systems. To this indispensible task, we now turn.
We have already discussed time evolution in the context of qubit ...