# 2015 Cushing Prize Lecturer: Giovanni Valente

"Relativistic Causality and Local Disentanglement in Quantum Field Theory"

Entanglement between distant quantum systems poses two outstanding problems in philosophy of quantum mechanics. First, the ensuing non-local correlations seem to entail a conflict with relativistic causality, namely the requirement that no causal process can propagate faster than light. That raises a threat of inconsistency with Einstein’s theory of Special Relativity. Second, the presence of entanglement undermines the possibility of achieving a division of the microscopic world into independent subsystems. In this talk, I will discuss these problems within the framework of algebraic relativistic quantum field theory. I will begin by distinguishing between two formulations of relativistic causality: that is, no superluminal signaling and no superluminal propagation of matter and energy carried by a field. I will then argue that the condition of Local Primitive Causality guarantees that quantum fields cannot propagate faster than light; furthermore, I will show how one can prove a no-superluminal-signaling theorem in terms of the notion of local operations. Finally, I will address the question whether a quantum field system can be isolated from its entanglement with other spacelike separated systems by acting on it by means of a local operation: in particular, I will demostrate that local disentanglement can be achieved in relativistic quantum field theory, thereby fulfilling a necessary condition for the mutual independence of microscopic subsystems.