Quantum indeterminacy

Quantum indeterminacy is the feature of quantum theory in which measurement outcomes are generally predicted by probabilities rather than uniquely determined in advance.

Born rule: The rule that converts a quantum state's amplitudes into probabilities for measurement outcomes. It specifies how quantum states yield the probabilities central to indeterminacy.
Determinism: The thesis that a complete state of the world and its laws fix every later state. Quantum outcome probabilities appear to challenge unique prediction from a complete physical description.
Bell's theorem: A theorem showing that correlations predicted by quantum theory cannot be reproduced by local hidden-variable models. It rules out a broad class of local explanations for quantum outcome probabilities.
Max Planck: A German physicist whose 1900 work on blackbody radiation introduced energy quantization. His quantization hypothesis began the theoretical shift that eventually made quantum probabilities necessary.
Quantum interpretation: A framework for explaining what quantum theory's mathematical states and predictions mean physically. Interpretations give different accounts of why a measurement has one particular outcome.
Quantum state: A mathematical description that encodes the probabilities of possible outcomes for a quantum system. Its amplitudes determine which outcomes are possible and how likely they are.
Hidden-variable theory: A class of theories that adds variables to quantum states to account for measurement outcomes. These theories test whether quantum probabilities reflect deeper, inaccessible physical facts.
Bell test: An experiment that tests whether measured correlations violate a Bell inequality. Observed violations constrain deterministic hidden-variable accounts of quantum statistics.
Niels Bohr: A Danish physicist who developed an influential model of the atom and helped shape quantum theory's interpretation. His complementarity framework emphasized the role of measurement conditions in quantum descriptions.
Measurement problem: The tension between continuous quantum evolution and the definite outcomes observed in measurements. It asks how probabilistic predictions relate to the single outcomes experiments record.

Linked from 5 pages