Eliminating reservoir density-of-states fingerprints in Coulomb blockade spectroscopy

TL;DR

This paper proposes techniques to eliminate reservoir density-of-states fingerprints in Coulomb blockade spectroscopy, improving the clarity of quantum dot excited-state resonances for quantum computing applications.

Contribution

It introduces a pump-probe spectroscopic method and a DC Coulomb blockade approach to suppress reservoir-DOS features in conductance maps.

Findings

Pump-probe spectroscopy effectively suppresses reservoir-DOS fingerprints.

The proposed DC method can eliminate DOS-related features in Coulomb blockade spectroscopy.

These techniques enhance the identification of quantum dot excited states.

Abstract

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.