A prerequisite for exploiting spins for quantum data storage and processing is long spin coherence times. Phosphorus dopants in silicon (Si:P) have been favoured as hosts for such spins because of measured electron spin coherence times (T2) longer than any other electron spin in the solid state: 14 ms at 7 K. Heavier impurities such as bismuth in silicon (Si:Bi) could be used in conjunction with Si:P for quantum information proposals that require two separately addressable spin species. However, the question of whether the incorporation of the much less soluble Bi into Si leads to defect species that destroy coherence has not been addressed. Here we show that schemes involving Si:Bi are indeed feasible as the electron spin coherence time T2 exceeds 1 ms at 10 K. We polarized the Si:Bi electrons and hyperpolarized the I=9/2 nuclear spin of 209Bi, manipulating both with pulsed magnetic resonance. The larger nuclear spin means that a Si:Bi dopant provides a 20-dimensional Hilbert space rather than the four dimensional Hilbert space of an I=1/2 Si:P dopant.
@article{arxiv.1004.3522,
title = {Initializing, manipulating and storing quantum information with bismuth dopants in silicon},
author = {Gavin W. Morley and Marc Warner and A. Marshall Stoneham and P. Thornton Greenland and Johan van Tol and Christopher W. M. Kay and Gabriel Aeppli},
journal= {arXiv preprint arXiv:1004.3522},
year = {2013}
}