Hybridization and spin decoherence in heavy-hole quantum dots

TL;DR

This paper theoretically explores how band hybridization affects spin decoherence in heavy-hole quantum dots, revealing tunable decoherence times and conditions to suppress hyperfine interactions, advancing quantum dot spin qubit control.

Contribution

It demonstrates that band hybridization causes exponential decay of hole-spin superpositions and shows how to tune decoherence times over many orders of magnitude.

Findings

Hyperfine-mediated nuclear pair flips cause exponential decay of hole-spin superpositions.

Decoherence time T2 can be tuned significantly by external parameters.

Conditions exist to suppress hyperfine interactions, enabling operation beyond the hyperfine limit.

Abstract

We theoretically investigate the spin dynamics of a heavy hole confined to an unstrained III-V semiconductor quantum dot and interacting with a narrowed nuclear-spin bath. We show that band hybridization leads to an exponential decay of hole-spin superpositions due to hyperfine-mediated nuclear pair flips, and that the accordant single-hole-spin decoherence time T2 can be tuned over many orders of magnitude by changing external parameters. In particular, we show that, under experimentally accessible conditions, it is possible to suppress hyperfine-mediated nuclear-pair-flip processes so strongly that hole-spin quantum dots may be operated beyond the `ultimate limitation' set by the hyperfine interaction which is present in other spin-qubit candidate systems.