  Applications of quantum mechanics rely on the accuracy of reading and writing
data. This requires accurate measurements and preparations of the quantum
states. I show that accurate measurements and preparations are impossible if
the total Hamiltonian is bounded from below (as thought to be in our universe).
This result invites a reevaluation of the limitations of quantum control,
quantum computing, and other quantum technologies dependent on the accuracy of
quantum preparations and measurements, and maybe of the assumption that the
Hamiltonian is bounded from below.
