Wigner’s Friend: Memory, Awareness and Observer-Dependent Realities

Abstract

In this
paper we analyze the Extended Wigner’s Friend Scenario as presented by Baumann
& Brukner. The conclusion—that awareness of any change in the Friend’s
‘internal record’ is impossible—is argued to follow from the no-signaling
principle. However, we show that this conclusion relies on combining two
contradictory assumptions: 1) the lab is perfectly isolated, and 2) Wigner is a
super-observer with complete control over the lab. Accepting both implies that
the Friend’s ‘record’ is quantum erased, making awareness impossible by
definition. To model awareness properly, we introduce a notebook—a stable,
unerasable record of the Friend’s measurement result. This notebook forces a
rejection of at least one of the original assumptions, resulting in a
fundamentally different physical context. We demonstrate how this change
affects the wavefunctions and joint measurement probabilities, revealing that
Baumann & Brukner’s reasoning effectively compares outcomes across
incompatible contexts. Next, we investigate the physical nature of observers
and measurements, proposing a more realistic model in which an observer’s state
consists of many quantum subsystems. Perfect isolation or complete control
becomes implausible, and naturally leads stabilization of the state of the
observer. These stable systems constitute an objective reality accessible to
other observers, while unstable, erasable systems remain subjective and
observer-relative. Our analysis supports an observer-dependent stance on facts
in quantum mechanics, where both subjective and objective realities can
coexist. This aligns closely with Relational Quantum Mechanics and provides a
consistent framework for interpreting Wigner’s Friend-type scenarios.