Hyperfine interaction induced decoherence of electron spins in quantum dots

TL;DR

This paper analyzes how hyperfine interactions cause decoherence in electron spins within quantum dots, showing that increasing nuclear polarization or magnetic fields alters decoherence dynamics, with implications for quantum computing stability.

Contribution

It provides a detailed analytical and numerical study of nuclear spin bath effects on electron spin decoherence in quantum dots, highlighting the impact of polarization and magnetic fields.

Findings

Decoherence dynamics shift from smooth decay to damped oscillations with increased nuclear polarization or magnetic field.

High nuclear polarization significantly prolongs decoherence times, but requires very large polarization levels.

Methods like dynamical decoupling may be more practical for suppressing decoherence than increasing polarization.

Abstract

We investigate in detail, using both analytical and numerical tools, the decoherence of electron spins in quantum dots (QDs) coupled to a bath of nuclear spins in magnetic fields or with various initial bath polarizations, focusing on the longitudinal relaxation in low and moderate field/polarization regimes. An increase of the initial polarization of nuclear spin bath has the same effect on the decoherence process as an increase of the external magnetic field, namely, the decoherence dynamics changes from smooth decay to damped oscillations. This change can be observed experimentally for a single QD and for a double-QD setup. Our results indicate that substantial increase of the decoherence time requires very large bath polarizations, and the use of other methods (dynamical decoupling or control of the nuclear spins distribution) may be more practical for suppressing decoherence of QD-based qubits.