Entanglement Swapping and Action at a Distance

Authors
Wharton, Ken 

Change log
Abstract

Abstract: A 2015 experiment by Hanson and Delft colleagues provided further confirmation that the quantum world violates the Bell inequalities, being the first Bell test to close two known experimental loopholes simultaneously. The experiment was also taken to provide new evidence of ‘spooky action at a distance’. Here we argue for caution about the latter claim. The Delft experiment relies on entanglement swapping, and our main claim is that this geometry introduces an additional loophole in the argument from violation of the Bell inequalities to action at a distance: the apparent action at a distance may be an artifact of ‘collider bias’. In the absence of retrocausality, the sensitivity of such experiments to this ‘Collider Loophole’ (CL) depends on the temporal relation between the entanglement swapping measurement C and the two measurements A and B between which we seek to infer a causal connection. CL looms large if the C is in the future of A and B, but not if C is in the past. The Delft experiment itself is the intermediate case, in which the separation is spacelike. We argue that this leaves it vulnerable to CL, unable to establish conclusively that it avoids it.

Publication Date
2021-11-03
Online Publication Date
Acceptance Date
2021-09-29
Keywords
Article, Nonlocality, Action at a distance, Entanglement swapping, Collider bias
Journal Title
Foundations of Physics
Journal ISSN
0015-9018
1572-9516
Volume Title
51
Publisher
Springer US