  In this paper we show how weak joint measurement and local feedback can be
used to control entanglement generation between two qubits. To do this, we make
use of a decoherence free subspace (DFS). Weak measurement and feedback can be
used to drive the system into this subspace rapidly. Once within the subspace,
feedback can generate entanglement rapidly, or turn off entanglement generation
dynamically. We also consider, in the context of weak measurement, some of
differences between purification and generating entanglement.
