The RT formula and its discontents: spacetime and entanglement

This essay is concerned with a number of related proposals that claim there is a link between spacetime topology and quantum entanglement. I indicate the extent to which these proposals can be understood as stating a duality, and then consider two general approaches to articulating such a duality: a “state-based” approach, under which one attempts to identify relevant topological states as dual to quantum entangled states; and an “observable-based” approach, under which one attempts to identify relevant topological observables as dual to quantum entangement observables. Both approaches are faced with issues, essentially due to the ambiguous nature of quantum entanglement, that remain to be addressed.