A No-Go Theorem for Observer-Independent Facts

Area of Science:

• Quantum mechanics
• Foundations of physics
• Quantum information theory

Background:

• Wigner's friend thought experiment explores quantum measurement and observer roles.
• Different observers (Wigner and his friend) have distinct accounts of quantum processes.
• Observable outcomes like detector clicks are considered 'facts'.

Purpose of the Study:

• To derive a no-go theorem for observer-independent facts.
• To analyze the implications of this theorem in the context of quantum theory self-consistency.
• To explore the relational nature of quantum observational statements.

Main Methods:

• Derivation of a no-go theorem for observer-independent facts (based on arXiv:1507.05255).
• Analysis of the derived theorem in conjunction with Frauchiger and Renner's result (arXiv:1604.07422) on single-world interpretations.
• Interpretation of 'self-consistency' in quantum theory as the comparability of observer statements within a single framework.

Main Results:

• A no-go theorem demonstrates the impossibility of observer-independent facts.
• Quantum theory's 'self-consistency' is shown to be incompatible with the assumption of universally comparable observational statements.
• The determinacy of observational statements is relative to the observer, suggesting a relational quantum framework.

Conclusions:

• Observer-independent facts are incompatible with the principles of quantum mechanics.
• Single-world interpretations of quantum theory face challenges related to self-consistency and observer relativity.
• Quantum reality is best understood through a relational perspective, where facts are observer-dependent.