In many electron spin qubit systems coherent control is impaired by the fluctuating nuclear spin bath of the host material. Previous experiments have shown dynamic nuclear polarization with feedback to significantly prolong the inhomogeneous dephasing time T2∗ by narrowing the distribution of nuclear Overhauser field fluctuations. We present a model relating the achievable narrowing of the Overhauser field to both the pump rate and the noise magnitude and find reasonable agreement with experimental data. It shows that former experiments on gated GaAs quantum dots were limited by the pump rate of the pumping mechanism used. Here we propose an alternative feedback scheme using electron dipole spin resonance. Sequentially applying two ac electric fields with frequencies slightly detuned from the desired Larmor frequency results in a pump curve with a stable fixed point. Our model predicts that T2∗ values on the order of microseconds can be achieved.
@article{arxiv.1503.06879,
title = {Narrowing of the Overhauser field distribution by feedback-enhanced dynamic nuclear polarization},
author = {Stefanie Tenberg and Robert P. G. McNeil and Sebastian Rubbert and Hendrik Bluhm},
journal= {arXiv preprint arXiv:1503.06879},
year = {2015}
}