Isolation and Information Flow in Quantum Dynamics
From the structure of quantum dynamics for closed and open systems, we describe several general results about information flow between interacting systems, which can be expressed in diagrammatic form. Conditions on information flow (e.g., that no information is transferred from system A to system B) imply that the overall dynamical evolution has a particular structure. We also remark that one simple type of two-qubit interaction, the unitary CNOT gate, cannot be represented by local operations and a single simultaneous information exchange.
Schumacher, Benjamin and Westmoreland, Michael, "Isolation and Information Flow in Quantum Dynamics" (2012). Foundations of Physics 42(7): 926-931. Faculty Publications. Paper 279.
Foundations of Physics