*If we measure an observable <math>Q</math> of a physical state <math>\Psi</math>, the result of our measurement will be an eigenvalue <math>\lambda</math> for the operator <math>Q</math>. The probability that the measurement will yield the value <math>\lambda</math> is given by the norm-squared of the projection of <math>\Psi</math> onto the <math>\lambda</math>-eigenspace of <math>Q</math>. | *If we measure an observable <math>Q</math> of a physical state <math>\Psi</math>, the result of our measurement will be an eigenvalue <math>\lambda</math> for the operator <math>Q</math>. The probability that the measurement will yield the value <math>\lambda</math> is given by the norm-squared of the projection of <math>\Psi</math> onto the <math>\lambda</math>-eigenspace of <math>Q</math>. |