Obituary for a Flea

TL;DR

This paper critically analyzes the Landsman-Reuvers proposal for solving the quantum measurement problem, highlighting its conceptual and practical shortcomings and arguing it lacks sufficient physical grounding and promise.

Contribution

It provides an extensive critique of the Landsman-Reuvers proposal, identifying fundamental issues and challenges in solving the measurement problem from within quantum theory.

Findings

Objections rely on counterfactual reasoning and idealizations.

Challenges include interpreting small numbers, reproducing the Born rule, and the role of classical certainties.

Specific issues with the proposal include physical interpretation of the flea perturbation and slow collapse times.

Abstract

The Landsman-Reuvers proposal to solve the measurement problem from within quantum theory is extensively analysed. In favor of proposals of this kind, it is shown that the standard reasoning behind objections to solving the measurement problem from within quantum theory rely on counterfactual reasoning or mathematical idealisations. Subsequently, a list of objections/challenges to the proposal are made. Part of these objections are equally important for all attempts at solving the measurement problem, such as the problem of interpreting small numbers in the density matrix, the problem of reproducing the Born rule, the use of pure states as a tool to alleviate the interpretational issues of quantum states, and the necessity of introducing classical certainties which are not strictly present in quantum theory. The additional objections that are particular to the proposal, such as the physical interpretation/origin of the flea perturbation, the use of potentials to solve a dynamical problem, slow collapse times, the inability to handle unequal probabilities, and the dictatorial role of the flea perturbation, lead us to believe that the Landsman-Reuvers proposal is lacking in both physical grounding and theoretical promise. Finally, an overview is given of the challenges that were encountered in this attempt to solve the measurement problem from within quantum theory.