SQAM_Spin Qubits in Artificial Molecules

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A key requirement for quantum information technology is the realisation of quantum bits where quantum information can be stored and manipulated on timescales much longer than the time needed for processing operations. Spins confined within optically active semiconductor quantum dots are highly promising candidates for this task due to their superior optical properties, the ease with which they can be integrated into optoelectronic devices and the availability of optical techniques for quantum state initialisation, control and readout. Here, we propose to investigate the dynamics of spins in pairs of coupled quantum dots, so-called quantum dot molecules (QDMs), a structure that supports highly robust and controllable multi-spin qubits. Specific project tasks include the development of novel and tailored quantum hardware based on optically active single spin (electron or hole) and double spin qubits confined to electrically controllable QDM devices.The German group has developed state-of-the-art techniques in nanostructure growth by molecular beam epitaxy, nanofabrication and spectroscopy (photoluminescence, Hahn echo, photon correlations, resonance fluorescence), while the Polish group has extensive expertise in advanced theory and modelling (k.p methods, quantum optics, open system dynamics). These complementary capabilities will be combined to develop a comprehensive understanding of the spin dynamics of QDMs, as well as of the interaction of spins with their environment, in particular in combination with external magnetic and electric fields which can be used to control the quantum states.Understanding the spin dynamics is crucial for controlling the loss of quantum information to the solid-state environment. Thus, the successful realisation of this project will enable prototypes of distributed quantum coherent networks with applications in information processing and secure communication.Reaching the project goals is only possible by working in a theory-experiment feedback loop involving manufacturing, characterisation and modelling. Therefore, the proposed research requires combining the highly complementary capabilities of the two contributing groups with world-leading expertise and capabilities in experimental and theoretical solid-state physics.