We investigate the performance of dynamical decoupling methods at suppressing electron spin decoherence from a low-temperature nuclear spin reservoir in a quantum dot. The controlled dynamics is studied through exact numerical simulation, with emphasis on realistic pulse delays and long-time limit. Our results show that optimal performance for this system is attained by a periodic protocol exploiting concatenated design, with control rates substantially slower than expected from the upper spectral cutoff of the bath. For a known initial electron spin state, coherence can saturate at long times, signaling the creation of a stable ``spin-locked'' decoherence-free subspace. Analytical insight on saturation is obtained for a simple echo protocol, in good agreement with numerical results.
@article{arxiv.cond-mat/0701507,
title = {Dynamical control of electron spin coherence in a quantum dot},
author = {Wenxian Zhang and V. V. Dobrovitski and Lea F. Santos and Lorenza Viola and B. N. Harmon},
journal= {arXiv preprint arXiv:cond-mat/0701507},
year = {2009}
}