Y2

Problem 9.3 Suppose Q interacts with an external environment E according to Eq. 9.1, and suppose the net effect of this is to leave every pure initial Q-state fixed: 10) ($1 - Id) ($1 . Show that the same dynamics will also preserve any entangled state between Q and a bystander system R. In the language of Section 7.5, an evolution that preserves Type I quantum information will also preserve Type II quantum information