Electrical Spin Driving by g-Matrix Modulation in Spin-Orbit Qubits

A collaboration with CEA-Leti (Grenoble)

In a semiconductor spin qubit with sizable spin-orbit coupling, coherent spin rotations can be driven by a resonant gate-voltage modulation. Recently, we have exploited this opportunity in the experimental demonstration of a hole spin qubit in a silicon device. Here we investigate the underlying physical mechanisms by measuring the full angular dependence of the Rabi frequency, as well as the gate-voltage dependence and anisotropy of the hole g factor. We show that a g-matrix formalism can simultaneously capture and discriminate the contributions of two mechanisms so far independently discussed in the literature: one associated with the modulation of the g factor, and measurable by Zeeman energy spectroscopy, the other not. Our approach has a general validity and can be applied to the analysis of other types of spin-orbit qubits.
Read more in A. Crippa et al. Phys. Rev. Lett. 120, 137702 (2018)






Gate-reflectometry dispersive readout and coherent control of a spin qubit in silicon

A collaboration with Institut Néel (Grenoble) and CEA-Leti (France)

Gate reflectometry map.
Silicon spin qubits have emerged as a promising path to large-scale quantum processors. In this prospect, the development of scalable qubit readout schemes involving a minimal device overhead is a compelling step. Here we report the implementation of gate-coupled rf reflectometry for the dispersive readout of a fully functional spin qubit device. We use a p-type double-gate transistor made using industry-standard silicon technology. The first gate confines a hole quantum dot encoding the spin qubit, the second one a helper dot enabling readout. The qubit state is measured through the phase response of a lumped-element resonator to spin-selective interdot tunneling. The demonstrated qubit readout scheme requires no coupling to a Fermi reservoir, thereby offering a compact and potentially scalable solution whose operation may be extended above 1 K.
Read more in A. Crippa et al. Nature Comm. 10, 2776 (2019)