Optimal feedback control of two-qubit entanglement in dissipative environments

We study the correction of errors intervening in two-qubit dissipating into their own environments. This is done by resorting to local feedback actions with the aim of preserving as much as possible the initial amount of entanglement. Optimal control is found by first gaining insights from the subsystem purity and then by numerical analysis on the concurrence. This is tantamount to a double optimization, on the actuation and on the measurement processes. Repeated feedback action is also investigated, thus paving the way for a continuous time formulation and solution of the problem.