On-demand electrical control of spin qubits

TL;DR

This paper introduces a switchable, electrically controlled method for manipulating spin qubits in silicon quantum dots without micromagnets, significantly enhancing control speed and fidelity for scalable quantum computing.

Contribution

The authors demonstrate a novel technique for electrically controlling spin-orbit interactions in silicon quantum dots, enabling fast, high-fidelity qubit operations without magnetic elements.

Findings

Achieved coherence time of approximately 50 microseconds.

Demonstrated single-qubit gates with 3 nanoseconds duration and 99.93% fidelity.

Enabled on-demand electrical control compatible with CMOS manufacturing.

Abstract

Once called a "classically non-describable two-valuedness" by Pauli , the electron spin is a natural resource for long-lived quantum information since it is mostly impervious to electric fluctuations and can be replicated in large arrays using silicon quantum dots, which offer high-fidelity control. Paradoxically, one of the most convenient control strategies is the integration of nanoscale magnets to artificially enhance the coupling between spins and electric field, which in turn hampers the spin's noise immunity and adds architectural complexity. Here we demonstrate a technique that enables a \emph{switchable} interaction between spins and orbital motion of electrons in silicon quantum dots, without the presence of a micromagnet. The naturally weak effects of the relativistic spin-orbit interaction in silicon are enhanced by more than three orders of magnitude by controlling the energy quantisation of electrons in the nanostructure, enhancing the orbital motion. Fast electrical control is demonstrated in multiple devices and electronic configurations, highlighting the utility of the technique. Using the electrical drive we achieve coherence time $T_{2,{\rm Hahn}}\approx50 \mu$s, fast single-qubit gates with ${T_{\pi/2}=3}$ ns and gate fidelities of 99.93 % probed by randomised benchmarking. The higher gate speeds and better compatibility with CMOS manufacturing enabled by on-demand electric control improve the prospects for realising scalable silicon quantum processors.