Strain engineering in Ge/GeSi spin qubits heterostructures

TL;DR

This paper explores how strain engineering in Ge/GeSi heterostructures can modify g-factors of heavy-hole spin qubits, enhancing control and operational flexibility for quantum computing applications.

Contribution

It demonstrates that uniaxial strains can significantly alter in-plane g-factors, enabling improved spin manipulation and device performance.

Findings

Uniaxial strains can increase in-plane g-factors above unity.

Etched mesa structures induce inhomogeneous strains in heterostructures.

Strain engineering broadens magnetic field operational range for spin qubits.

Abstract

The heavy-holes in Ge/GeSi heterostructures show highly anisotropic gyromagnetic response with in-plane $g$-factors $g_{x,y}^*\lesssim 0.3$ and out-of-plane $g$-factor $g_z^*\gtrsim 10$. As a consequence, Rabi hot spots and dephasing sweet lines are extremely sharp and call for a careful alignment of the magnetic field in Ge spin qubit devices. We investigate how the $g$-factors can be engineered by strains. We show that uniaxial strains can raise in-plane $g$-factors above unity while leaving $g_z^*$ essentially constant. We discuss how the etching of an elongated mesa in a strained buffer can actually induce uniaxial (but inhomogeneous) strains in the heterostructure. This broadens the operational magnetic field range and enables spin manipulation by shuttling holes between neighboring dots with different $g$-factors.