No-signaling condition and quantum dynamics - art. no. 170405

We show that the basic dynamical rules of quantum physics can be derived fr om its static properties and the condition that superluminal communication is forbidden. More precisely, the fact that the dynamics has to be describe d by linear completely positive maps on density matrices is derived from th e following assumptions: (1) physical states are described by rays in a Hil bert space, (2) probabilities for measurement outcomes at any given time ar e calculated according to the usual trace rule, and (3) superluminal commun ication is excluded. This result also constrains possible nonlinear modific ations of quantum physics.