The Quantum Rashomon Effect: A Strengthened Frauchiger-Renner Argument
Jochen Szangolies
TL;DR
The paper addresses whether quantum theory can consistently describe its own use in multi-agent settings and strengthens the Frauchiger–Renner argument by introducing a state-independent, three-agent scenario that avoids entanglement and final collapse. It employs a Peres–Mermin–Wigner construction to derive deterministic contradictions under standard assumptions, highlighting that a single, globally consistent narrative cannot capture all observers' perspectives. The core proposal reframes the conflict through epistemic horizons, positing that observers have finite, overlapping but non-commensurable information about a system, which prevents a universal meta-narrative. This quantum-perspectivist view implies a fundamental Rashomon effect intrinsic to quantum reasoning, with potential implications for interpretations, experimental tests in quantum information, and our understanding of objectivity in quantum mechanics.
Abstract
The Frauchiger-Renner argument aims to show that `quantum theory cannot consistently describe the use of itself': in many-party settings where agents are themselves subject to quantum experiments, agents may make predictions that contradict observations. Here, we introduce a simplified setting using only three agents, that is independent of the initial quantum state, thus eliminating in particular any need for entanglement, and furthermore does not need to invoke any final measurement and resulting collapse. Nevertheless, the predictions and observations made by the agents cannot be integrated into a single, consistent account. We propose that the existence of this sort of \emph{Rashomon effect}, i.e. the impossibility of uniting different perspectives, is due to failing to account for the limits put on the information available about any given system as encapsulated in the notion of an \emph{epistemic horizon}.