Coherent feedback that beats all measurement-based feedback protocols
Kurt A. Jacobs, Xiaoting Wang, Howard M. Wiseman · New Journal of Physics · 2014
We show that when the speed of control is bounded, there is a widely applicable minimal-time control problem for which a coherent feedback protocol is optimal, and is faster than all measurement-based feedback protocols, where the latter are defined in a strict sense. The superiority of the coherent protocol is due to the fact that it can exploit a geodesic path in Hilbert space, a path that measurement-based protocols cannot follow.