Sergey Frolov, Delft University of Technology
Abstract
Electron spin is a natural quantum two-level system with long coherence times. This makes spin the leading candidate for solid state quantum computing. A big challenge is to find a practical way of controlling spin on the nanoscale. For instance, magnetic fields are hard to generate on a chip, especially at high frequencies desired for quantum computing. A much preferred control knob is the one that was the key to success for charge-based electronics – a gate voltage or an electric field. It turns out that in semiconductors it is possible to couple spin to electric fields. Through spin-orbit interaction we can control spin by simply moving the electron around. I will describe a spin-orbit qubit that we have realized in an InAs nanowire. We confined single electrons to quantum dots and performed coherent spin manipulation using electric fields. The phase of gigahertz microwave signals was used to implement two-axis qubit control, and the difference in g-factors was used to selectively address nearby qubits. Decoherence due to fluctuating nuclear spins remains a serious challenge for this type of qubit, but coherence can alrady be extended using dynamical decoupling techniques.