We propose that quantum entanglement is a special sort of selection artefact, explicable as a combination of (i) collider bias and (ii) a boundary constraint on the collider variable. We show that the proposal is valid for a special class of (`W-shaped') Bell experiments involving delayed-choice entanglement swapping, and argue that it can be extended to the ordinary (`V-shaped') case. The proposal requires no direct causal influence outside lightcones, and may hence offer a way to reconcile Bell nonlocality and relativity. The main argument is a detailed version of an approach previously outlined in arXiv:2404.13928 [quant-ph].
We propose that quantum entanglement is a special sort of selection artefact, explicable as a combination of (i) collider bias and (ii) a boundary constraint on the collider variable. We show that the proposal is valid for a special class of (W-shaped') Bell experiments involving delayed-choice entanglement swapping, and argue that it can be extended to the ordinary (V-shaped') case. The proposal requires no direct causal influence outside lightcones, and may hence offer a way to reconcile Bell nonlocality and relativity. The main argument is a detailed version of an approach previously outlined in arXiv:2404.13928 [quant-ph].
In previous work with Ken Wharton, it was proposed that Bell correlations are a special sort of selection artefact, explained by a combination of (i) collider bias and (ii) a boundary constraint on the collider variable. This requires no direct causal influence outside lightcones, and may hence offer a new way to reconcile Bell nonlocality and relativity. This piece outlines a new argument for the proposal. It explains how it is valid for a special class of ('W-shaped') Bell experiments involving delayed-choice entanglement swapping, and argues that it can be extended to the general ('V-shaped') case. A detailed version of the argument is now available in arXiv:2406.04571 [quant-ph].
We propose a mechanism for quantum entanglement. The key ingredient is the familiar statistical phenomenon of collider bias, or Berkson's bias. In the language of causal models a collider is a variable causally influenced by two or more other variables. Conditioning on a collider typically produces non-causal associations between its contributing causes, even if they are actually independent. It is easy to show that this phenomenon can produce associations analogous to Bell correlations, in suitable post-selected ensembles. It is also straightforward that such collider artefacts may become real connections, resembling causality, if a collider is 'constrained' (e.g., by a future boundary condition). We consider the time-reversed analogues of these points in the context of retrocausal models of QM. Retrocausality yields a collider at the source of an EPR-Bell particle pair, and in this case constraint of the collider is possible by normal methods of experimental preparation. It follows that connections resembling causality may be expected to emerge across such colliders, from one branch of the experiment to the other. Our hypothesis is that this constrained retrocausal collider bias is the origin of entanglement. The piece is written for a general audience, and is based on a suggestion first made in arXiv:2101.05370 [quant-ph].
In this piece, written for a general audience, we propose a mechanism for quantum entanglement. The key ingredient is collider bias. In the language of causal models, a collider is a variable causally influenced by two or more other variables. Conditioning on a collider typically produces non-causal correlations between its contributing causes. This phenomenon can produce associations analogous to Bell correlations, in suitable post-selected ensembles. Such collider artefacts may become real connections, resembling causality, if a collider is 'constrained' (e.g., by a future boundary condition). We consider the time-reversed analogues of these points in the context of retrocausal models of QM. Retrocausality yields a collider at the source of an EPR-Bell particle pair, and in this case constraint of the collider is possible by normal methods of experimental preparation. It follows that connections resembling causality may emerge across such colliders, from one branch of the experiment to the other. Our hypothesis is that this constrained retrocausal collider bias is the origin of entanglement. This piece is based on a suggestion first made in arXiv:2101.05370v4 [quant-ph], and is an ancestor of an essay now published online in Aeon magazine [Price & Wharton 2023a]. In an updated version of the argument in arXiv:2309.10969 [quant-ph] we (i) demonstrate its application in a real Bell experiment; and (ii) show that we can do without an explicit postulate of retrocausality
We show that Bell correlations may arise as a special sort of selection artefact, produced by ordinary control of the initial state of the experiments concerned. This accounts for nonlocality, without recourse to any direct spacelike causality or influence. The argument improves an earlier proposal in (arXiv:2101.05370v4 [quant-ph], arXiv:2212.06986 [quant-ph]) in two main respects: (i) in demonstrating its application in a real Bell experiment; and (ii) in avoiding the need for a postulate of retrocausality. This version includes an Appendix, discussing the relation of the proposal to the conclusions of Wood and Spekkens (arXiv:1208.4119 [quant-ph]).
In this piece, written for a general audience, we propose a mechanism for quantum entanglement. The key ingredient is the familiar statistical phenomenon of collider bias, or Berkson's bias. In the language of causal models a collider is a variable causally influenced by two or more other variables. Conditioning on a collider typically produces non-causal associations between its contributing causes, even if they are actually independent. It is easy to show that this phenomenon can produce associations analogous to Bell correlations, in suitable post-selected ensembles. It is also straightforward that such collider artefacts may become real connections, resembling causality, if a collider is 'constrained' (e.g., by a future boundary condition). We consider the time-reversed analogues of these points in the context of retrocausal models of QM. Retrocausality yields a collider at the source of an EPR-Bell particle pair, and in this case constraint of the collider is possible by normal methods of experimental preparation. It follows that connections resembling causality may be expected to emerge across such colliders, from one branch of the experiment to the other. Our hypothesis is that this constrained retrocausal collider bias is the origin of entanglement. The piece is based on a suggestion first made in arXiv:2101.05370 [quant-ph].
In this piece, written for a general audience, we propose a mechanism for quantum entanglement. The key ingredient is the familiar statistical phenomenon of collider bias, or Berkson's bias. In the language of causal models, a collider is a variable causally influenced by two or more other variables. Conditioning on a collider typically produces non-causal associations between its contributing causes, even if they are actually independent. It is easy to show that this phenomenon can produce associations analogous to Bell correlations, in suitable post-selected ensembles. It is also straightforward that such collider artefacts may become real connections, resembling causality, if a collider is 'constrained' (e.g., by a future boundary condition). We consider the time-reversed analogues of these points in the context of retrocausal models of QM. Retrocausality yields a collider at the source of an EPR-Bell particle pair, and in this case constraint of the collider is possible by normal methods of experimental preparation. It follows that connections resembling causality may be expected to emerge across such colliders, from one branch of the experiment to the other. Our hypothesis is that this constrained retrocausal collider bias is the origin of entanglement. The piece is based on a suggestion we first made in arXiv:2101.05370v4 [quant-ph].