A Stronger Theorem Against Macro-realism

TL;DR

This paper presents a new, stronger no-go theorem against macro-realism in quantum theory, using ontological models to address loopholes in previous Leggett-Garg-based arguments.

Contribution

It introduces a novel approach employing ontological models to establish a more robust no-go theorem against macro-realism.

Findings

Provides a stronger theoretical proof ruling out macro-realism

Addresses and closes loopholes in Leggett-Garg inequalities

Utilizes ontological models for foundational quantum analysis

Abstract

Macro-realism is the position that certain "macroscopic" observables must always possess definite values: e.g. the table is in some definite position, even if we don't know what that is precisely. The traditional understanding is that by assuming macro-realism one can derive the Leggett-Garg inequalities, which constrain the possible statistics from certain experiments. Since quantum experiments can violate the Leggett-Garg inequalities, this is taken to rule out the possibility of macro-realism in a quantum universe. However, recent analyses have exposed loopholes in the Leggett-Garg argument, which allow many types of macro-realism to be compatible with quantum theory and hence violation of the Leggett-Garg inequalities. This paper takes a different approach to ruling out macro-realism and the result is a no-go theorem for macro-realism in quantum theory that is stronger than the Leggett-Garg argument. This approach uses the framework of ontological models: an elegant way to reason about foundational issues in quantum theory which has successfully produced many other recent results, such as the PBR theorem.