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SQAM_Spin Qubits in Artificial Molecules

Subject Area Experimental Condensed Matter Physics
Theoretical Condensed Matter Physics
Term from 2017 to 2020
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 381446053
 
Final Report Year 2024

Final Report Abstract

The project supported by the Polish-German funding initiative “Beethoven 2” focused on exploring spin-qubits in optically active semiconductor quantum dot (QD) nanostructures. This included the exploration of electron- and hole-spin qubits in single optically active QDs, as well as few-spin systems in electrically tunable QD-molecules. Spins qubits in optically active semiconductor QDs are of interest due to their superior optical properties, the ease with which they can be integrated into optoelectronic devices as well as the availability of quantum optical techniques for state initialization, control and readout. The project was successful with major scientific results including: (i) The development of an understanding of the mechanisms for quantum light emission from QDs, inclduing the factors limiting the quantum indistringuishability of emitted photons, (ii) The identification of the origin of antibunching in resonance fluorescence , (iii) The exploration of resonaance fluorescence spectral dynamics of a single QD modulated via time dependent strain fields, and (iv) The development of new methods to significantly enhance both the quantum state indistinguishability and statistics of emitted photons, including code that was made freely available. We also (v) developed a theory of the two-photon interference arising from dissimilar quantum light sources and (vi) explored spin qubits in coupled QD-molecules as planned. In this context, the project succeeded to build QD-molecule devices with optical control of charge status (1e, 2e, 1h, 2h) and explore their coherent quantum optical response. Finally, a book chapter was written summarizing the current state of the art in electron and hole spin relaxation in self-assembled QD nanostructures in collaboration with te polish collaborators. The project resulted in more than ten publications and book chapters, some of which involved the Polish partners. In summary, the advances made in materials physics, understsanding of the dephasing properties of spin-qubits and quantum optical properites of single and coupled QD-nanostructures fed into several subsequently started projects funded by BMBF, the European Union and the Bavrian Ministry of Science and Arts. Scientiic collaborations between the Polish and German partners are ongoing, most recently concerning the role of acoustic phonons in the relaxation and dephasing of spin and orbital states in QD-molecules.

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