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Glossary

Quantum glossary

Born rule

The rule that the probability of a measurement outcome is the squared magnitude of its amplitude.

It is the only bridge between the mathematics of amplitudes and what an experiment records. Every histogram you get from a simulator or a real device is sampled according to it.

P(x) = |⟨x|ψ⟩|²

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Related terms

  • Amplitude — The complex number attached to each possible outcome of a quantum state; its squared magnitude is that outcome’s probability.
  • Measurement — Reading out a qubit, which returns a classical bit sampled by the Born rule and leaves the qubit in the state matching it.