Title: How ubiquitous is entanglement in QFT?

Abstract: It is well known that entanglement is ubiquitous in quantum field theory: even the simplest states within the simplest field theories are highly entangled. The foundation of this statement rests on two results: (1) the Reeh-Schlieder theorem,  which shows that all field variables in any one region of spacetime are entangled with variables in other regions, and (2) the calculations of entanglement entropy between a region and its complement, which show that entanglement between adjoining spacetime regions is not just large but UV divergent. In this talk, I will argue that these results do not provide much information about the entanglement between individual local degrees of freedom.  I will then present a way of quantifying such entanglement, involving only a finite number of degrees of freedom, finite regions of space, and quantities that are directly measurable. I will summarize our understanding both in (1+D)-dimensional Minkowski spacetime and de Sitter spacetime, paying special attention to the consequences of the latter in our ability to detect quantum effects from the inflationary era.