Relational quantum mechanics

Relational quantum mechanics is an interpretation in which physical properties are definite only relative to interactions between physical systems, not as observer-independent values.

Quantum measurement: A physical interaction in which a quantum system becomes correlated with a measuring system and yields a definite outcome relative to it. Measurement outcomes are facts for interacting systems, rather than global properties shared by every system.
Quantum mechanics: A physical theory describing matter and radiation through quantum states, probability amplitudes, and measurement outcomes. Relational quantum mechanics interprets this theory without changing its standard empirical predictions.
Carlo Rovelli: An Italian theoretical physicist known for work on quantum gravity and for proposing relational quantum mechanics. Rovelli introduced the interpretation in 1996 to address the meaning of quantum states and measurement.
Quantum reference frames: Frameworks for describing quantum systems relative to other quantum systems that serve as reference frames. They offer mathematical tools for analyzing how physical descriptions change between systems.
Quantum state: A mathematical representation used to calculate probabilities for the outcomes of measurements on a quantum system. In this interpretation, a state describes information relative to a system, not an absolute condition.
Physical system: A defined portion of the physical world treated as a unit for describing interactions and properties. The interpretation assigns properties only in relation to another physical system.
Interpretations of quantum mechanics: Accounts of what quantum theory says about physical reality beyond its mathematical predictions. Relational quantum mechanics is one interpretation among competing accounts of quantum theory.
Relationalism: The philosophical view that certain properties or facts exist only through relations among entities. The interpretation applies relationalism to physical properties and quantum events.
Quantum entanglement: A quantum relationship in which the joint state of multiple systems cannot be described as a product of separate states. Correlations between systems can establish facts relative to one system without making them universal.
Interaction (physics): A physical process in which systems influence one another and acquire correlations or exchange conserved quantities. Interactions are the events at which relational facts become definite.

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