SiSPIN · Silicon Platform for Quantum Spintronics

Quantum spintronics aims at utilizing the quantum nature of individual spins to bring new functionalities into logic circuits, either to make classical information processing more efficient or to implement spin-based quantum algorithms. Two critical aspects for quantum spintronics are a long spin coherence time and a strong, tunable spin-orbit interaction for fast electrical manipulation of spins. Up to now, experiments have mainly focused on III-V semiconductor nanostructures, where hyperfine coupling with nuclear spins limits electron-spin coherence. Low nuclear spin materials, and in particular group-IV semiconductors, were found to be a natural alternative. However, in most of the currently studied group-IV based systems, spin-orbit coupling is very weak, preventing fast electrical manipulation of spins.We propose to investigate a new direction based on p-type SiGe nanostructures. This system has the unique combination of low hyperfine and strong spin-orbit couplings. Aside from developing demonstrator devices such as spin-filters or single spin qubits, we aim at exploring recently proposed schemes for long range spin-spin coupling, an essential requirement for scalable qubit circuits. To investigate hole-spin dynamics and achieve quantum spintronic functionalities, novel types of concepts will be experimentally investigated (spin-polarized helical states, spin-orbit mechanisms for spin-selective tunneling and long-range spin-spin coupling, etc.). Because of the higher complexity of hole-type systems, a dedicated theoretical framework will be developed in support to experiments. In addition to a bottom-up approach which has been successful in providing nanowire and quantum-dot heterostructures, we shall realize SiGe quantum devices by means of state-of-the-art CMOS technology. This will allow us to know how spin-based functionalities demonstrated in bottom-up nanostructures can be implemented into a truly scalable silicon platform.