  Decoherence is the main problem to be solved before quantum computers can be
built. To control decoherence, it is possible to use error correction methods,
but these methods are themselves noisy quantum computation processes. In this
work we study the ability of Steane's and Shor's fault-tolerant recovering
methods, as well a modification of Steane's ancilla network, to correct errors
in qubits. We test a way to measure correctly ancilla's fidelity for these
methods, and state the possibility of carrying out an effective error
correction through a noisy quantum channel, even using noisy error correction
methods.
