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Extended Wigner's Friend Scenarios (EWFSs) go beyond the standard usage ofquantum theory, where agents are treated classically, and instead model agentsas unitary evolving quantum systems. This has been the subject of several no-goresults: Frauchiger and Renner (FR) suggested that quantum agents reasoningusing quantum theory will arrive at logical paradoxes, while other resultshighlight challenges for having an objective notion of measurement events andfor causal reasoning in EWFSs. This raises the question: Is it possible toreliably make and test scientific predictions, and consistently reason aboutthe world when applying quantum theory universally without assuming thatobserved measurement outcomes are absolute? We give a positive answer bydeveloping a general quantum circuit framework for EWFSs. We formalise theconcept of Heisenberg cuts by mapping them to distinct channels in a quantumcircuit, and prove that FR-type paradoxes can be fully resolved by makingexplicit the conditioning on the quantum channels that are used in thereasoning process. We provide concrete rules by which quantum agents can reasonand make predictions in a logically and causally consistent manner. Ourframework describes all perspectives and predictions of an EWFS within asingle, well-defined causal structure, although it allows events to befundamentally subjective. Moreover, we show that an objective notion ofmeasurement events nevertheless emerges in real-world experiments. Thisdemonstrates the possibility of a relational yet operational frameworkovercoming challenges to scientific reasoning in EWFSs without modifying theBorn rule, quantum unitarity, or the axioms of classical logic and probabilitytheory. This enables analysis of different EWFS arguments and provides aplatform to consistently extend quantum information methods and studies toWigner's Friend Scenarios.

A general quantum circuit framework for Extended Wigner's Friend  Scenarios: logically and causally consistent reasoning without absolute  measurement events