  It is shown that if one can perform a restricted set of fast manipulations on
a quantum system, one can implement a large class of dynamical evolutions by
effectively removing or introducing selected Hamiltonians. The procedure can be
used to achieve universal noise-tolerant control based on purely unitary
open-loop transformations of the dynamics. As a result, it is in principle
possible to perform noise-protected universal quantum computation using no
extra space resources.
