On-demand electrical control of spin qubits

Once called a “classically non-describable two-valuedness” by Pauli, the electron spin is a natural stage for long-lived quantum information since it is mostly impervious to electric noise. This immunity comes at the price of limiting the options for implementing gate operations in spin-based quantum computation – paradoxically, the most scalable control strategy is the exploitation of relativistic spin-orbit effects to couple spins back to electric fields. We have developed a technique to create switchable interaction between spins and orbital motion of electrons in silicon quantum dots. The naturally weak effects of spin-orbit interaction in silicon are enhanced by more than three orders of magnitude by controlling the energy quantisation of the electron in the nanostructure, enhancing the orbital motion within the quantum dot. The enhanced electrical control is demonstrated in multiple devices and electronic configurations, endorsing the applicability of this technique for large arrays of qubits. We are able to achieve decoherence times of T2,Hahn ≈ 50 μs, single qubit π/2-gates as fast as Tπ/2 = 3 ns and gate fidelities of 99% probed by randomised benchmarking. Solving this dilemma in Silicon creates a strong perspective for scalability of quantum processors.