A "thoughtful" Local Friendliness no-go theorem: a prospective experiment with new assumptions to suit

Abstract

A recent paper by two of us and co-workers, based on an extended Wigner's friend scenario, demonstrated that certain empirical correlations predicted by quantum theory (QT) violate inequalities derived from a set of metaphysical assumptions we called "Local Friendliness" (LF). These assumptions are strictly weaker than those used for deriving Bell inequalities. Crucial to the theorem was the premise that a quantum system with reversible evolution could be an observer (colloquially, a "friend"). However, that paper was noncommittal on what would constitute an observer for the purpose of an experiment. Here, we present a new LF no-go theorem which takes seriously the idea that a system's having *thoughts* is a sufficient condition for it to be an observer. Our new derivation of the LF inequalities uses four metaphysical assumptions, three of which are thought-related, including one that is explicitly called "Friendliness". These four assumptions, in conjunction, allow one to derive LF inequalities for experiments involving the type of system that "Friendliness" refers to. In addition to these four metaphysical assumptions, this new no-go theorem requires two assumptions about what is *technologically* feasible: Human-Level Artificial Intelligence, and Universal Quantum Computing which is fast and large scale. The latter is often motivated by the belief that QT is universal, but this is *not* an assumption of the theorem. The intent of the new theorem is to give a clear goal for future experimentalists, and a clear motivation for trying to achieve that goal. We review various approaches to QT in light of our theorem. The popular stance that "quantum theory needs no interpretation" does not question any of our assumptions and so is ruled out. Finally, we quantitatively discuss how difficult the experiment we envisage would be, and briefly discuss milestones on the paths towards it.

44 pages, 3 figures. Accepted for publication in <Q>uantum

References in corpus (17)

• Quantum Computing
• Surface codes: Towards practical large-scale quantum computation
• Semiconductor Qubits In Practice
• The Future of Quantum Computing with Superconducting Qubits
• No extension of quantum theory can have improved predictive power
• Efficient Distributed Quantum Computing
• Dynamically Generated Logical Qubits
• Focus beyond quadratic speedups for error-corrected quantum advantage
• Studying ultrafast Rabi dynamics with a short-wavelength seeded free-electron laser
• The Moral Consideration of Artificial Entities: A Literature Review
• Surface code compilation via edge-disjoint paths
• Stable Facts, Relative Facts
• No-go theorem based on incomplete information of Wigner about his friend
• A local pre-decoder to reduce the bandwidth and latency of quantum error correction
• A possibilistic no-go theorem on the Wigner's friend paradox
• Quantum-accelerated constraint programming
• Freely Scalable Quantum Technologies using Cells of 5-to-50 Qubits with Very Lossy and Noisy Photonic Links

Cited by in corpus (16)

• Assessing and Advancing the Potential of Quantum Computing: A NASA Case Study
• Relating Wigner's Friend Scenarios to Nonclassical Causal Compatibility, Monogamy Relations, and Fine Tuning
• The measurement postulates of quantum mechanics are not redundant
• Wigner's friend's memory and the no-signaling principle
• Classical information and collapse in Wigner's friend setups
• Local Friendliness Polytopes In Multipartite Scenarios
• Extended Wigner's friend paradoxes do not require nonlocal correlations
• Quantum measurements and equilibration: the emergence of objective outcomes via entropy maximisation
• Connecting extended Wigner's friend arguments and noncontextuality
• Wigner's friend scenarios: on what to condition and how to verify the predictions
• Perspectives in and on Quantum Theory
• Quantum interpretations, causality and quantum computation
• Limits of Absoluteness of Observed Events in Timelike Scenarios: A No-Go Theorem
• Towards violations of Local Friendliness with quantum computers
• On the significance of Wigner's Friend in contexts beyond quantum foundations
• Quantum Superpositions of Conscious States in a Minimal Integrated Information Model