Abstract
Three-terminal tunnelling experiments on quantum dots in the Coulomb-blockade regime allow a quantitative determination of the coupling strength of individual quantum states to the leads. Exploiting this insight, we have observed independent fluctuations of the coupling strengths as a function of electron number and magnetic field due to changes in the shape of the wave function in the dot. Such a detailed understanding and control of the dot-lead coupling can be extended to more complex systems such as coupled dots, and are essential for building functional quantum electronic systems.