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Two Paths to the Parisian Zigzag

In 1953 O. Costa de Beauregard, a student of de Broglie, raised an objection to the EPR argument. Einstein, Podolsky and Rosen had assumed that there is no action at a distance; “that would be magic”, as Schrödinger said at the time. Costa de Beauregard pointed out that the quantum world might allow spacelike causal influence, without such magic, so long as the influence took a zigzag path via the intersecting past light cones of the measurements in question. This suggestion is related to the so-called ‘retrocausal’ loophole in Bell’s Theorem, but like that loophole it receives little attention, and remains poorly understood. In this talk I present a new argument for Costa de Beauregard’s zigzag (now generalized in recent work by Leifer and Pusey), and discuss its relation to the motivation stemming from EPR and Bell.