What Does '(Non)-Absoluteness of Observed Events' Mean?

Abstract: Recently there have emerged an assortment of theorems relating to the 'absoluteness of emerged events,' and these results have sometimes been used to argue that quantum mechanics may involve some kind of metaphysically radical non-absoluteness, such as relationalism or perspectivalism. However, in our view a close examination of these theorems fails to convincingly support such possibilities. In this paper we argue that the Wigner's friend paradox, the theorem of Bong et al and the theorem of Lawrence et al are all best understood as demonstrating that if quantum mechanics is universal, and if certain auxiliary assumptions hold, then the world inevitably includes various forms of 'disaccord,' but this need not be interpreted in a metaphysically radical way; meanwhile, the theorem of Ormrod and Barrett is best understood either as an argument for an interpretation allowing multiple outcomes per observer, such as the Everett approach, or as a proof that quantum mechanics cannot be universal in the sense relevant for this theorem. We also argue that these theorems taken together suggest interesting possibilities for a different kind of relational approach in which dynamical states are relativized whilst observed events are absolute, and we show that although something like 'retrocausality' might be needed to make such an approach work, this would be a very special kind of retrocausality which would evade a number of common objections against retrocausality. We conclude that the non-absoluteness theorems may have a significant role to play in helping converge towards an acceptable solution to the measurement problem.

• The paper challenges the notion that quantum disaccord necessitates radical relationalism by demonstrating that observed events can remain absolute.
• It critically examines key theorems including Wigner’s Friend and Bong et al., delineating different types of measurement disaccord among observers.
• The analysis underscores that auxiliary assumptions in quantum mechanics can yield observer disaccord without mandating metaphysically non-absolutist interpretations.

An Insightful Examination of Non-Absoluteness Theorems in Quantum Mechanics

The paper "What Does '(Non)-Absoluteness of Observed Events' Mean?" by Emily Adlam provides a comprehensive analysis of several quantum mechanics theorems that suggest the non-absoluteness of observed events, investigating their implications for interpretations of quantum theory. The study primarily dissects the Wigner’s Friend paradox, and the theorems of Bong et al., Lawrence et al., and Ormrod and Barrett, questioning whether these results necessarily imply a metaphysically radical departure from the conventional understanding that observed events are absolute. Adlam argues that the non-absoluteness suggested by these theorems does not necessarily lead to a requirement for radically relational or perspectival interpretations and instead proposes an understanding of dynamic states as relational while maintaining the absoluteness of observed events.

Overview of Key Arguments and Theorems

The paper examines the concept of 'absoluteness of observed events,' which has been the subject of much debate in quantum mechanics. Some interpretations suggest these theorems imply that even observed events are not absolute and depend on individual observers. Particularly, interpretations like the Everett or multiple-outcome-per-observer (MOPO) approaches allow for multiple outcomes per observer. However, the non-absoluteness theorems have also been used to argue for a single-outcome-per-observer interpretation where different observers may disagree on the outcome.

Adlam critiques this line of reasoning by closely examining the capabilities and implications of the discussed theorems. She proposes that while these theorems demonstrate that universality and specific auxiliary assumptions in quantum mechanics can lead to ‘disaccord’—situations in which observers disagree about measurement results—this disaccord does not necessarily require relationalism as a fundamental feature of reality. Instead, Adlam suggests that interpretations might focus more on a dynamically relational approach where dynamical states vary relative to observers, while maintaining that observed events themselves are absolute and observer-independent.

Technical Analysis of Scenarios and Responses

1. Wigner's Friend Paradox: This paradox suggests potential contradictions in measurement outcomes when a quantum system is described within the framework of universal quantum mechanics. Adlam argues this setup can indicate Type-II disaccord—disagreement over inferences about another observer’s experiences—without requiring observers to adopt radically relational perspectives.
2. Bong et al. Theorem: Addressing this theorem's implications, Adlam separates absoluteness of observed events into two components (AOE1 and AOE2) and discusses Type-III disaccord where, even when measurements yield a single outcome, different observers may have differing access influencing correlations between their observations. This disaccord provides an argument for some form of non-locality or retrocausal influences, challenging common objections to these concepts due to their failure to produce logical contradictions.
3. Lawrence et al. and Ormrod and Barrett Theorems: These are explored for their implication of possible outcomes’ indifference without resorting to absolute retrocausal dependence. Instead, any relational structure must be reconciled with a broader framework that doesn’t degrade to epistemic incoherency.

Relational Dynamical States and Future Insights

Adlam concludes that these theorems suggest viable paths for dynamically relational interpretations of quantum mechanics, devoid of severe metaphysical commitments toward non-absoluteness. She highlights two interpretations—Relational Quantum Mechanics with cross-perspective links and Kent’s Lorentzian solution—illustrating compatibility with non-relativized absolute events, yet exhibiting Type-II disaccord. Importantly, Adlam stresses the relevance of subtle retrocausal and non-local adjustments that align predictions robustly with universal unitary quantum mechanics across differently contextualized observer perspectives.

Implications and Future Directions

The work underscores that non-absoluteness within quantum mechanics need not lead us to adopt radical philosophically non-traditional positions. It challenges researchers to further investigate the balance between absolute observed events and relational dynamical interactions, potentially diverging from many-worlds-like scenarios without hypothesizing metaphysically extreme realities.

These conclusions forge a path for quantum mechanics interpretations that preserve the empirical integrity of observed outcomes amid complex relational dynamics. Adlam’s exploration invites deeper consideration of the interplay between dynamics, observation, and relational aspects inherent in quantum mechanical systems, proposing they undoubtedly deserve more attention in forthcoming theoretical advancements.