In quantum mechanics, particle-system phase-space states have probabilities. States that do not happen have as much information as states that do happen. In quantum mechanics, because they had probability to happen, states that did not happen {counterfactual, quantum mechanics} can cause physical events/states on the same or other particles, because they collapse the wavefunction without interacting with the particle property/event/state. Measuring for a particle state that does not happen {null measurement} {interaction-free measurement} can gain information about another system particle or state without affecting that particle or state.
Physical Sciences>Physics>Quantum Mechanics>States
5-Physics-Quantum Mechanics-States
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Date Modified: 2022.0224