Quantum Amplitudes and Probabilities

The qubit state vector contains amplitudes rather than measurement probabilities.

The amplitudes belong to waves, because in quantum mechanics, the behavior of quantum particles is described by wave functions.

Waves have three characteristics:

• The wavelength is the distance over which the wave’s shape repeats.
• The phase of a wave is the position on the waveform cycle at a certain point.
• The amplitude of a wave is the distance between its center and its crest.

The following figure depicts these three characteristics.