A Stronger Theorem Against Macro-realism

• Main Authors: John-Mark A. Allen, Owen J. E. Maroney, Stefano Gogioso
• Format: Article
• Language: English
• Published: Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften 2017-07-01
• Series: Quantum
• Online Access: https://quantum-journal.org/q-2017-07-14-13/pdf/

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 do not 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.