Optimal operation of hole spin qubits

TL;DR

This paper experimentally identifies optimal magnetic field orientations, called 'sweetlines', in hole spin qubits that minimize charge noise sensitivity while enabling fast, efficient control, advancing scalable quantum computing architectures.

Contribution

It demonstrates the existence and tunability of 'sweetlines' in hole spin qubits, enhancing coherence and control for scalable quantum processors.

Findings

Identification of 'sweetlines' where qubits are insensitive to charge noise

Achieved Rabi oscillations with quality factors up to 1200

Moderate gate voltage adjustments can tune the sweetlines

Abstract

Hole spins in silicon or germanium quantum dots have emerged as a compelling solid-state platform for scalable quantum processors. Besides relying on well-established manufacturing technologies, hole-spin qubits feature fast, electric-field-mediated control stemming from their intrinsically large spin-orbit coupling [1, 2]. This key feature is accompanied by an undesirable susceptibility to charge noise, which usually limits qubit coherence. Here, by varying the magnetic-field orientation, we experimentally establish the existence of ``sweetlines'' in the polar-azimuthal manifold where the qubit is insensitive to charge noise. In agreement with recent predictions [3], we find that the observed sweetlines host the points of maximal driving efficiency, where we achieve fast Rabi oscillations with quality factors as high as 1200. Furthermore, we demonstrate that moderate adjustments in gate voltages can significantly shift the sweetlines. This tunability allows multiple qubits to be simultaneously made insensitive to electrical noise, paving the way for scalable qubit architectures that fully leverage all-electrical spin control. The conclusions of this experimental study, performed on a silicon metal-oxide-semiconductor device, are expected to apply to other implementations of hole spin qubits.