This is a vague statement that could mean two different things.
1. That quantum mechanics is deterministic (as far as wavefunctions go) and time-reversible. Knowing the state of a system at any given point, you can use the differential equation (Schrodinger's equation) that determines the evolution of the system, to find the state any other time.
2. The should in the statement is referring to the philosphical idea that we expect that the true laws of physics will always be deterministic and time-reversible.
1. That quantum mechanics is deterministic (as far as wavefunctions go) and time-reversible. Knowing the state of a system at any given point, you can use the differential equation (Schrodinger's equation) that determines the evolution of the system, to find the state any other time.
2. The should in the statement is referring to the philosphical idea that we expect that the true laws of physics will always be deterministic and time-reversible.