A Stronger Theorem Against Macro-realism

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.

Accepted journal version. 10 + 7 pages, 1 figure

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Cited by in corpus (7)

• Quantum Advantage from Sequential-Transformation Contextuality
• Comparing Conditions for Macrorealism: Leggett-Garg Inequalities vs No-Signaling in Time
• Optimal experimental demonstration of error-tolerant quantum witnesses
• Subtleties of witnessing quantum coherence in non-isolated systems
• A review and reformulation of macroscopic realism: resolving its deficiencies using the framework of generalized probabilistic theories
• Constraints on Macroscopic Realism Without Assuming Non-Invasive Measurability
• Reality, Causality, and Quantum Theory