Terahertz Charge and Spin Manipulation in Quantum Dots – TERADOT

The dynamics of electron transport in quantum nanostructures has recently received a great attention, in particular due to the possibility to manipulate quantum states on time scales smaller than the relaxation and decoherence times, a requirement for quantum information processing. In this fields, quantum dots are particularly interesting since they can trap single electrons which can then be individually addressed either electrically or optically. For this reason quantum dots have received lots of attention in the last few years as a playground for studying the limits of quantum mechanics on the single particle level, as well as a building block for quantum information processing.

In this project we propose to study experimentally the coherent manipulation of electronic states in a semiconductor quantum dot at terahertz frequency. The frequency range we want to explore (from 100 GHz to 1 THz) is intermediate between microwave and optical frequencies. The aim of the project is first to deepen the understanding of high frequency manipulation of single charges and single spins in quantum dots, on time and energy scales that have been very poorly explored before. We will concentrate more particularly on the spin degree of freedom, which has recently received a great attention due to the large expectation for quantum information processing. By combining the high frequency and quantum dots with large spin orbit interaction, the goal of the project is to demonstrate fast electrical manipulation of a single spin, on a time scale that will allow quantum error correction processes to operate, which has still not been demonstrated for semiconductor quantum dots.

The reason why this frequency range has been poorly explored before for quantum systems is related to the technical difficulty of integrating a terahertz source with a carefully shielded cryo-magnetic environment. For this purpose we will propose an original solution based on photo-generation of terahertz and integrated high frequency electronics. A second challenge of the project will be the use of quantum dots in materials with strong spin-orbit interaction, which will be achieved using InAs and InSb nanowires, which are very new in the field of quantum electronics. While several requirements of the project have been demonstrated separately in the literature, e.g. generation of terahertz in the appropriate frequency range, quantum dots from InAs nanowires, the main difficulty will be to combine these already challenging results into a single experiment. For this purpose the strength of the project is the composition of the team, which will assemble complementary young researchers that have already demonstrated high level results on each of these fields.