The performance of multi-electron spin qubits is examined by comparing exchange oscillations in coupled single-electron and multi-electron quantum dots in the same device. Fast (> 1 GHz) exchange oscillations with a quality factor Q > 15 are found for the multi-electron case, compared to Q ~ 2 for the single-electron case, the latter consistent with previous experiments. A model of dephasing that includes voltage and hyperfine noise is developed that is in good agreement with both single- and multi-electron data, though in both cases additional exchange-independent dephasing is needed to obtain quantitative agreement across a broad parameter range.
@article{arxiv.1306.2720,
title = {Coherence and Screening in Multi-Electron Spin Qubits},
author = {A. P. Higginbotham and F. Kuemmeth and M. P. Hanson and A. C. Gossard and C. M. Marcus},
journal= {arXiv preprint arXiv:1306.2720},
year = {2014}
}
Comments
Supplemental Material here: https://dl.dropboxusercontent.com/u/1742676/Higg_Supplement.pdf