Incoherent control and entanglement for two-dimensional coupled systems
Raffaele Romano, Domenico D’Alessandro · Physical Review A · 2006
We investigate accessibility and controllability of a quantum system $S$ coupled to a quantum probe $P$, both described by two-dimensional Hilbert spaces, under the hypothesis that the external control affects only $P$. In this context accessibility and controllability properties describe to what extent it is possible to drive the state of the system $S$ by acting on $P$ and using the interaction between the two systems. We give necessary and sufficient conditions for these properties and we discuss the relation with the entangling capability of the interaction between $S$ and $P$. In particular, we show that controllability can be expressed in terms of the SWAP and $\sqrt{\mathrm{SWAP}}$ operators acting on the composite system.