What is an amplitude?
The number a qubit holds for each possible result. Squaring it gives the chance of that result.
An amplitude of 0.6 for 1 means a 0.36 chance, or 36%, of measuring 1. Since the chances must add up to 100%, the squared amplitudes of a qubit always add up to 1.
Unlike a probability, an amplitude can be negative. Two amplitudes of opposite sign cancel when they combine, the way two waves cancel in noise-cancelling headphones. In real hardware amplitudes are complex numbers, which adds phase.
In the lessonsSee it in a simulation
Related
- QubitThe basic unit of a quantum computer: it can be 0, 1, or a blend of both until it is measured.
- SuperpositionA qubit state that is a blend of 0 and 1, with an amplitude for each.
- MeasurementReading a qubit. It returns 0 or 1 at random, with chances set by the squared amplitudes, and ends the blend.
- InterferenceAmplitudes adding up or cancelling when they combine. Quantum algorithms use it to make wrong answers unlikely.
- PhaseThe part of an amplitude beyond its size. It decides how amplitudes add up or cancel.