The Leggett-Garg inequality, named for Anthony James Leggett and Anupam Garg, is an inequality that any macrorealistic physical theory must obey. Macrorealism combines two assumptions: that a macroscopic object with two or more distinguishable states is always definitely in one of them, and that a system's state can in principle be determined without disturbing it or its later behavior. Experiments that violate the inequality, as quantum-mechanical systems can, show that at least one of these two classical assumptions fails to hold for the system actually being measured.
Facts
StatementA mathematical inequality fulfilled by all macrorealistic physical theories, where macrorealism is the conjunction of two postulates: macrorealism per se (a macroscopic object with two or more distinct states is at any given time in a definite one of them) and noninvasive measurability (the state can in principle be determined without effect on the state itself or on the subsequent dynamics). Quantum mechanics violates the inequality. 2 Classification
Statement Form Connections
Has Statement Form
Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.
Sources
1. Wikipedia: Leggett-Garg inequality
WikipediaLead section, statement-form referenceQuote, Lead section, statement-form reference
The Leggett-Garg inequality, named for Anthony James Leggett and Anupam Garg, is a mathematical inequality fulfilled by all macrorealistic physical theories.
2. Leggett-Garg inequality, Wikipedia
Lead paragraphQuote, Lead paragraph
is a mathematical inequality fulfilled by all macrorealistic physical theories.
3. Leggett and Garg, Quantum mechanics versus macroscopic realism, Physical Review Letters 54, 857
Publication line of the article pageQuote, Publication line of the article page
Published 4 March, 1985
Reader Challenges (0)
No disputes yet. Spotted an error or a better source? Open the first one.
Sign in to dispute this or suggest a correction.