Introduction
Important to the development of efficient adaptive quantum design algorithms is the existence of realistic physical models. It is essential that these models capture all the key degrees of freedom available and provide an accurate representation of the actual physical processes in the device. This requires detailed knowledge which may not be readily available. For devices, it is the responsibility of the device physicist to provide the required understanding and develop the needed models. By way of example, the following link is a chapter detailing aspects of nonequilibrium electron transport and its role in determining the high-frequency performance of HBTs.