  We indicate that there are points to keep in mind in utilizing quantum states
prepared by the adiabatic quantum computation. Even if an instantaneous
expectation value of a physical quantity for the adiabatically prepared quantum
state is close to an expectation value for the true vacuum, this does not
assure us that the prepared vacuum is close to the true vacuum. In general time
average of the expectation value tend to systematically differ from the true
value. Using a simple model we discuss how to diminish this systematic
difference.
