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The informational observer in Relational Quantum Mechanics

Bethany Terris

Abstract

Relational Quantum Mechanics (RQM) treats quantum states as observer-dependent facts rather than absolute properties. While this relational stance is conceptually attractive, it raises concerns about empirical confirmation, particularly in multi-observer scenarios. Existing responses within RQM focus on securing agreement between observers by strengthening the status, stability, or accessibility of recorded outcomes. However, they leave open a more basic question: what grounds the persistence of an observer across time? Scientific observation presupposes stable records and the capacity to relate outcomes across successive measurements. We argue that the minimal definition of the observer in RQM as a merely interacting physical system is insufficient to support this requirement. We propose a complementary account of the observer that distinguishes physical interaction from informational coherence, and show how this distinction supports empirical confirmation in Wigner's friend-type scenarios.

The informational observer in Relational Quantum Mechanics

Abstract

Relational Quantum Mechanics (RQM) treats quantum states as observer-dependent facts rather than absolute properties. While this relational stance is conceptually attractive, it raises concerns about empirical confirmation, particularly in multi-observer scenarios. Existing responses within RQM focus on securing agreement between observers by strengthening the status, stability, or accessibility of recorded outcomes. However, they leave open a more basic question: what grounds the persistence of an observer across time? Scientific observation presupposes stable records and the capacity to relate outcomes across successive measurements. We argue that the minimal definition of the observer in RQM as a merely interacting physical system is insufficient to support this requirement. We propose a complementary account of the observer that distinguishes physical interaction from informational coherence, and show how this distinction supports empirical confirmation in Wigner's friend-type scenarios.
Paper Structure (11 sections, 14 equations, 1 figure)

This paper contains 11 sections, 14 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Rethinking the Observer
  3. The problem of the minimalist observer in RQM
  4. Building a complementary account of the observer
  5. Structural Coherence from Sequential Weak Values
  6. Coherent records
  7. Sequential weak values reveal coherence
  8. Agreement and Confirmation in the Wigner's Friend Paradox
  9. Wigner and his friend cannot agree with each other
  10. Two-step confirmation model
  11. Conclusion

Figures (1)

  • Figure 1: The Wigner's friend paradox: A friend inside of a closed laboratory $L$ measures a qubit and obtains a definite outcome. Wigner is outside $L$ and sees the entire laboratory in a superposition of states. The perspectives of Wigner and his friend appear to contradict each other.