Contents Quantum information processing (QIP) requires qubits that are characterized by robustness to the surrounding environment and scalability [1]. Here we investigate two different types of quantum dots in view of addressing the two problems of robustness and scalability. Although the electron spin in self assembled quantum dots (QDs) has proven to be a good candidate for QIP [2], it is very susceptible to feedback from the surrounding nuclear spin bath with serious limitations in the coherence [3]. Hole spins on the other hand, because of symmetry arguments are more robust and have been shown to be excellent candidates for the creation of universal 1 qubit gates [4]. Up to now, positive charging of the dots is been done by the utilization of diode structures through sequential charging with limitations coming from noise of the external electric fields [5]. Here we grew p-type -doped InAs QDs and investigated spin pumping properties with a traditional two and a new one-laser scheme [6]. Fig. 1(a) shows the level structure of the quantum dots investigated in this experiment while Fig. 1(b) shows the resonance of the spin pumping.
(a) Level structure of a positively charged dot with degenerate inner transitions (red arrows), allowing spin pumping and repumping with a single laser scheme. (b) Spin pump-repump resonance as seen from the counts of the detection channel. (c) Schematic representation of an InP site controlled nanowire quantum dot.
