Electron Spin Dephasing due to Hyperfine Interactions with a Nuclear Spin Bath

TL;DR

This paper develops a theory for electron spin dephasing caused by hyperfine interactions with a nuclear spin bath, especially at low magnetic fields, and compares it with experimental data in GaAs quantum dots.

Contribution

It introduces a new theoretical framework for decoherence due to hyperfine-mediated nuclear spin interactions at low magnetic fields.

Findings

Theory applicable down to B~10 mT

Explains spectral diffusion and hyperfine effects

Aligns with recent GaAs quantum dot experiments

Abstract

We investigate pure dephasing decoherence (free induction decay and spin echo) of a spin qubit interacting with a nuclear spin bath. While for infinite magnetic field B the only decoherence mechanism is spectral diffusion due to dipolar flip-flops of nuclear spins, with decreasing B the hyperfine-mediated interactions between the nuclear spins become important. We give a theory of decoherence due to these interactions which takes advantage of their long-range nature. For a thermal uncorrelated bath we show that our theory is applicable down to B~10 mT, allowing for comparison with recent experiments in GaAs quantum dots.