Tunable g factor and phonon-mediated hole spin relaxation in Ge/Si nanowire quantum dots

Abstract

We theoretically consider g factor and spin lifetimes of holes in a longitudinal Ge/Si core/shell nanowire quantum dot that is exposed to external magnetic and electric fields. For the ground states, we find a large anisotropy of the g factor which is highly tunable by applying electric fields. This tunability depends strongly on the direction of the electric field with respect to the magnetic field. We calculate the single-phonon hole spin relaxation times T1 for zero and small electric fields and propose an optimal setup in which very large T1 of the order of tens of milliseconds can be reached. Increasing the relative shell thickness or the longitudinal confinement length further prolongs T1. In the absence of electric fields, the dephasing vanishes and the decoherence time T2 is determined by T2 = 2 T1.

7 pages, 4 figures

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• Majorana Fermions in Ge/Si Hole Nanowires
• A natural heavy-hole flopping mode qubit in germanium
• Anisotropic Pauli spin blockade in hole quantum dots
• Acoustic phonons and strain in core/shell nanowires
• Exchange interaction of hole-spin qubits in double quantum dots in highly anisotropic semiconductors
• Strongly Interacting Holes in Ge/Si Nanowires
• A Multiscale Simulation Approach for Germanium-Hole-Based Quantum Processor