  The wave-function Monte-Carlo method, also referred to as the use of
"quantum-jump trajectories", allows efficient simulation of open systems by
independently tracking the evolution of many pure-state "trajectories". This
method is ideally suited to simulation by modern, highly parallel computers.
Here we show that Krotov's method of numerical optimal control, unlike others,
can be modified in a simple way, so that it becomes fully parallel in the pure
states without losing its effectiveness. This provides a highly efficient
method for finding optimal control protocols for open quantum systems and
networks. We apply this method to the problem of generating entangled states in
a network consisting of systems coupled in a unidirectional chain. We show that
due to the existence of a dark-state subspace in the network, nearly-optimal
control protocols can be found for this problem by using only a single
pure-state trajectory in the optimization, further increasing the efficiency.
