[Paper Review] Problems with Probability in Everett's Interpretation of Quantum Mechanics

Casey Blood|ArXiv.org|Jan 8, 2009

Quantum Mechanics and Applications15 references3 citations

TL;DR

This paper argues that the many-worlds interpretation (MWI) of quantum mechanics, as proposed by Everett, fails to account for the role of probability in observation. It contends that since MWI produces multiple observer branches without singling out one as the perceiving self, probability cannot be meaningfully assigned unless supplemented by mechanisms like hidden variables or wave function collapse to identify the actual observer experience.

ABSTRACT

In the many-worlds interpretations (MWIs) of Everett and others, if I am the observer, there are several versions of me but no version is singled out as the one corresponding to my perceptions. However, it can be shown that the probability law implies one version must be singled out. Thus MWIs do not provide a sufficient basis for probability. If we are to have an acceptable description of the physical universe, MWIs must be supplemented by some mechanism, such as hidden variables or collapse, that singles out one version of the observer as the perceiving version.

Motivation & Objective

• To challenge the adequacy of the many-worlds interpretation (MWI) in explaining the subjective experience of probability during quantum measurements.
• To highlight the contradiction in MWI where multiple observer branches exist but no branch is distinguished as the one experiencing the outcome.
• To argue that probability laws inherently require a singled-out observer, which MWI fails to provide without additional mechanisms.
• To propose that MWI must be supplemented with mechanisms such as hidden variables or wave function collapse to restore a coherent account of probability.
• To clarify and simplify the core objections to MWI, particularly regarding the measurement problem and the role of probability.

Proposed method

• Analyzing the structure of Everett's MWI, which posits that all quantum outcomes occur in branching universes.
• Identifying the absence of a mechanism to select one observer branch as the actual perceiving observer in MWI.
• Applying the logic of probability theory to show that probability implies a unique outcome experience, contradicting MWI's superposition of observer states.
• Using thought experiments to demonstrate that without a selection mechanism, probability assignments in MWI lack physical grounding.
• Comparing MWI with alternative interpretations that include collapse or hidden variables to emphasize the need for such additions.
• Revising and clarifying earlier arguments in version 3 to focus on the central issue: the incompatibility of probability with unselected branches.

Experimental results

Research questions

• RQ1 Can the many-worlds interpretation consistently account for the appearance of probabilistic outcomes in quantum measurements?
• RQ2 Why does the existence of multiple observer branches in MWI undermine the assignment of meaningful probabilities to measurement results?
• RQ3 What mechanism, if any, is required to single out one observer branch as the one experiencing the measurement outcome?
• RQ4 Is the concept of probability coherent within a framework that treats all branches as equally real and physically existing?
• RQ5 Can MWI be considered a complete physical theory without additional postulates such as wave function collapse or hidden variables?

Key findings

• The many-worlds interpretation does not provide a basis for probability because it generates multiple observer branches without selecting one as the actual perceiving observer.
• Probability laws require a unique outcome experience, which MWI fails to deliver due to the equal physical reality of all branches.
• The paper concludes that MWI must be supplemented with an additional mechanism—such as hidden variables or wave function collapse—to identify the observer experiencing a specific measurement result.
• The argument is strengthened in version 3 by simplifying and clarifying the core objections to MWI, focusing on the incompatibility of probability with unselected branches.
• Without such supplementation, the assignment of probabilities in MWI lacks physical meaning and cannot account for the subjective certainty of measurement outcomes.
• The analysis shows that the standard MWI framework cannot explain why an observer should experience one outcome with a specific probability rather than another.