Timelike entanglement for delayed-choice entanglement swapping

Experiments involving delayed-choice entanglement swapping seem to suggest that particles can become entangled after they’ve already been detected. This astonishing result is taken by some to undermine realism about entanglement. In this paper, I argue that one can offer a fully realist explanation of delayed-choice entanglement swapping by countenancing timelike entanglement relations. I argue that such an explanation—radical though it may be—isn’t incoherent and doesn’t invite paradox. I compare this approach to the antirealist alternative and a more deflationary realist strategy defended by Egg, each of which face certain challenges. The upshot is that we should take seriously the possibility of timelike entanglement and seek to develop a framework for quantum theory which allows for it.