  The differential conductance map of a single electron transistor (SET)
provides information about a variety of parameters related to (quantum) dots,
relevant for semiconductor-based quantum computing schemes. However, in
ultra-scaled device architectures, identification of excited-state resonances
of the quantum dot in the conductance map is often complicated by the
appearance of features due to non-uniform density-of-states (DOS) of the source
and drain reservoirs of the SET. Here, we demonstrate theoretically that the
pump-probe spectroscopic technique, originally introduced by Fujisawa et al.,
allows the fingerprint of the reservoir-DOS to be completely suppressed while
preserving the visibility of the excited state resonances. We also propose a
specific approach for performing DC Coulomb blockade spectroscopy, which can
effectively eliminate the DOS-related features. The advantages and limitations
of the two approaches are investigated in detail. The results demonstrated here
may provide an important optimization capability for emerging proposals of
computer-automated control of large arrays of coupled but independently
controlled charge and spin qubits.
