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Completely top-down hierarchical structure in quantum mechanics.
Yakir Aharonov1,2,3, Eliahu Cohen4,5, Jeff Tollaksen6,2
1Institute for Quantum Studies, Chapman University, Orange, CA 92866; yakir@post.tau.ac.il eli17c@gmail.com.
Complex quantum systems cannot be fully understood by examining their smallest parts. Higher-order quantum correlations can dictate lower-order ones, but not the reverse, suggesting a top-down structure.
Area of Science:
- Quantum mechanics
- Many-body systems
- Foundations of physics
Background:
- Investigates the limits of inductive reasoning in characterizing complex systems.
- Explores whether system behavior can be reduced to its fundamental components.
- Addresses the relationship between subsystem properties and overall system behavior.
Purpose of the Study:
- To determine if large quantum systems can be fully characterized by their subsystems.
- To investigate the reducibility of complex system behavior to atomic-level interactions.
- To analyze the nature of correlations in quantum mechanics.
Main Methods:
- Introduces a two-particle example demonstrating strong correlations.
- Applies concepts to atomic and electromagnetic systems.
- Develops a general construction using pre- and postselected ensembles.
Main Results:
- Demonstrates that higher-order quantum correlations can determine lower-order ones.
- Shows that lower-order correlations provide no information about higher-order correlations.
- Highlights that N-body correlations can be global properties under 'strictly local' measurements.
Conclusions:
- Answers the question of reducibility in the negative for specific systems and measurements.
- Supports a top-down structure in many-body quantum mechanics.
- Suggests that global properties can emerge from local constraints in quantum systems.

