  We study a protocol for two-qubit state guidance that does not rely on
feedback mechanisms. In our scheme, entanglement can be concentrated by
arranging the interactions of the qubits with a continuous variable ancilla. By
properly post-selecting the outcomes of repeated measurements of the state of
the ancilla, the qubit state is driven to have a desired amount of purity and
entanglement. We stress the primary role played by the first iterations of the
protocol. Inefficiencies in the detection operations can be fully taken into
account.
