Measurement in quantum mechanics

Quantum states describe probabilities, not certainties

In quantum physics, a quantum state mathematically describes a system, associating complex numbers called probability amplitudes to each point in space. Applying the Born rule to these amplitudes yields probabilities for the outcomes of measurements. This probabilistic nature means that quantum states cannot predict certainties but only probabilities.

Example

An electron's quantum state provides probabilities for its position and momentum, not definite locations or velocities.

Remember this

The probabilistic nature of quantum states is fundamental to understanding why a quantum superposition collapses to a definite state upon observation.

Text adapted from Wikipedia, licensed under CC BY-SA 4.0.

Related concepts

Copenhagen interpretation

Wavefunction collapse is fundamental

Aspect ratio (image)

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Bell's theorem

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Quantum decoherence

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Fermi paradox

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Eastin–Knill theorem

No quantum error correcting code can have a continuous symmetry acting transversely on physical qubits

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