Higginbotham, Andrew Patrick4; Kuemmeth, Ferdinand4; Hanson, M.P.2; Gossard, A.C.3; Marcus, Charles M.4
1 Condensed Matter Physics, The Niels Bohr Institute, Faculty of Science, Københavns Universitet2 unknown3 University of California Santa Barbara, Department of Materials4 Condensed Matter Physics, The Niels Bohr Institute, Faculty of Science, Københavns Universitet
Multielectron spin qubits are demonstrated, and performance examined by comparing coherent exchange oscillations in coupled single-electron and multielectron quantum dots, measured in the same device. Fast (>1 GHz) exchange oscillations with a quality factor Q ∼ 15 are found for the multielectron case, compared to Q ∼ 2 for the single-electron case, the latter consistent with experiments in the literature. A model of dephasing that includes voltage and hyperfine noise is developed that is in good agreement with both single- and multielectron data, though in both cases additional exchange-independent dephasing is needed to obtain quantitative agreement across a broad parameter range.