These waves have all the same properties of water waves, but the amplitude, or height of the wave, is a probability amplitude. This amplitude can be negative, which probably seems a little strange.

A probability is always positive (or zero) and real, but an amplitude can be positive, negative, or even complex (if you don't know what a complex number is, don't worry). This changes everything.

The best we can do is to calculate the probability of obtaining each possible outcome, according to what’s called the Born rule: The wave function assigns an “amplitude” to each measurement outcome, ...

Probability amplitude proportion of the excited corner states (IMAGE) Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS ...