© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

arXiv:1002.0906 · Studies in History and Philosophy of Science Part B Studies in History and Philosophy of Modern Physics

Does time-symmetry imply retrocausality? How the quantum world says “Maybe”?

Huw Price

Published Mar 3, 2012• 91 citations

DOI: 10.1016/j.shpsb.2011.12.003

Related papers

Special relativity not implying retrocausality

J. Domínguez-Montes, E. L. Eisman

Physics Essays•Aug 16, 2010•1 citation

Retrocausality and quantum mechanics

David Thomas Pegg

Studies in History and Philosophy of Science Part B Studies in History and Philosophy of Modern Physics•Aug 4, 2008•35 citations

Does Time-Symmetry Imply Retrocausality? How the Quantum World Says "Maybe"

Huw Price

It has often been suggested that retrocausality offers a solution to some of the puzzles of quantum mechanics: e.g., that it allows a Lorentz-invariant explanation of Bell correlations, and other manifestations of quantum nonlocality, without action-at-a-distance. Some writers have argued that time-symmetry counts in favour of such a view, in the sense that retrocausality would be a natural consequence of a truly time-symmetric theory of the quantum world. Critics object that there is complete time-symmetry in classical physics, and yet no apparent retrocausality. Why should the quantum world be any different? This note throws some new light on these matters. I call attention to a respect in which quantum mechanics is different, under some assumptions about quantum ontology. Under these assumptions, the combination of time-symmetry without retrocausality is unavailable in quantum mechanics, for reasons intimately connected with the differences between classical and quantum physics (especially the role of discreteness in the latter). Not all interpretations of quantum mechanics share these assumptions, however, and in those that do not, time-symmetry does not entail retrocausality.

•Jan 1, 2011•93 citations

Retrocausality & TGD

Matti Pitkänen

This article is inspired by the article "Is a time symmetric interpretation of quantum theory possible without retrocausality?" of Leifer and Pusey related to the notion of retrocausality. Retrocausality means the possibility of causal influences propagating in non-standard time direction. The conjecture is that retrocausality could allow wave functions to be real and allow to get rid of the problematic notion of state function reduction. TGD leads to a new view about reality of wave function solving the basic problem of quantum measurement theory. In ZEO quantum states are replaced by zero energy states analogous to pairs of initial and final states in ordinary positive energy ontology and can be regarded as superpositions of classical deterministic time evolutions. The sequence of state function reductions means a sequence of re-creations of the superpositions of classical realities identified as space-time surfaces. The TGD based view about scattering amplitudes has rather concrete connection with the view of Cramer as I interpret it. There is however no attempt to reduce quantum theory to a purely classical theory. The notion of the "world of classical worlds" (WCW) consisting of classical realities identified as space-time surfaces replaces space-time as a fixed observer independent reality in TGD. Retrocausality is basic aspect of TGD. Zero Energy Ontology (ZEO) predicts that both arrows of time are possible. In this sense TGD is time symmetric. On the other hand, twistor lift of TGD predicts a violation of time reflection T and this might imply that second arrow of causality dominates in some sense. The ZEO based view about state function reduction essential for TGD inspired theory of consciousness and implying generalized Zeno effect giving rise to conscious entities - "selves" - is also essential. One might say that when conscious entity dies it re-incarnates as time-reversed self.

Prespacetime journal•Sep 5, 2017•0 citations

Quantum Causality and Retrocausation: Revisiting Temporal Order in Quantum Physics

Adam Alzerkany

•Jan 1, 2025•4 citations

Quantum Mechanics and Retrocausality

David Atkinson

Astrophysics and space science library•Jan 1, 2000•1 citation

It has often been suggested that retrocausality offers a solution to some of the puzzles of quantum mechanics: e.g., that it allows a Lorentz-invariant explanation of Bell correlations, and other manifestations of quantum nonlocality, without action-at-a-distance. Some writers have argued that time-symmetry counts in favour of such a view, in the sense that retrocausality would be a natural consequence of a truly time-symmetric theory of the quantum world. Critics object that there is complete time-symmetry in classical physics, and yet no apparent retrocausality. Why should the quantum world be any different? This note throws some new light on these matters. I call attention to a respect in which quantum mechanics is different, under some assumptions about quantum ontology. Under these assumptions, the combination of time-symmetry without retrocausality is unavailable in quantum mechanics, for reasons intimately connected with the differences between classical and quantum physics (especially the role of discreteness in the latter). Not all interpretations of quantum mechanics share these assumptions, however, and in those that do not, time-symmetry does not entail retrocausality.

This article is inspired by the article "Is a time symmetric interpretation of quantum theory possible without retrocausality?" of Leifer and Pusey related to the notion of retrocausality. Retrocausality means the possibility of causal influences propagating in non-standard time direction. The conjecture is that retrocausality could allow wave functions to be real and allow to get rid of the problematic notion of state function reduction. TGD leads to a new view about reality of wave function solving the basic problem of quantum measurement theory. In ZEO quantum states are replaced by zero energy states analogous to pairs of initial and final states in ordinary positive energy ontology and can be regarded as superpositions of classical deterministic time evolutions. The sequence of state function reductions means a sequence of re-creations of the superpositions of classical realities identified as space-time surfaces. The TGD based view about scattering amplitudes has rather concrete connection with the view of Cramer as I interpret it. There is however no attempt to reduce quantum theory to a purely classical theory. The notion of the "world of classical worlds" (WCW) consisting of classical realities identified as space-time surfaces replaces space-time as a fixed observer independent reality in TGD. Retrocausality is basic aspect of TGD. Zero Energy Ontology (ZEO) predicts that both arrows of time are possible. In this sense TGD is time symmetric. On the other hand, twistor lift of TGD predicts a violation of time reflection T and this might imply that second arrow of causality dominates in some sense. The ZEO based view about state function reduction essential for TGD inspired theory of consciousness and implying generalized Zeno effect giving rise to conscious entities - "selves" - is also essential. One might say that when conscious entity dies it re-incarnates as time-reversed self.