Quantum states describe probabilities, not certainties
Image: Thierry Dugnolle, CC0, via Wikimedia Commons
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.
The probabilistic nature of quantum states is fundamental to understanding why a quantum superposition collapses to a definite state upon observation.
Related concepts
Copenhagen interpretation
Copenhagen: Wavefunction collapse upon observation creates reality
Aspect ratio (image)
Bell inequality violations confirm quantum nonlocality
Bell's theorem
Bell's theorem disproves local hidden-variable theories
Quantum decoherence
Quantum decoherence explains wavefunction collapse through environmental interaction
Fermi paradox
Information paradox questions black hole information fate
Eastin–Knill theorem
No quantum error correcting code can have a continuous symmetry acting transversely on physical qubits
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