The initialization and manipulation of quantum information stored in silicon by bismuth dopants.

ABSTRACT

A prerequisite for exploiting spins for quantum data storage and processing is long spin coherence times. Phosphorus dopants in silicon (SiP) 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 with isotopically purified silicon. Heavier impurities such as bismuth in silicon (SiBi) could be used in conjunction with SiP 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 SiBi are indeed feasible as the electron spin coherence time T2 is at least as long as for SiP with non-isotopically purified silicon. We polarized the SiBi electrons and hyperpolarized the I=9/2 nuclear spin of (209)Bi, manipulating both with pulsed magnetic resonance. The larger nuclear spin means that a SiBi dopant provides a 20-dimensional Hilbert space rather than the four-dimensional Hilbert space of an I=1/2 SiP dopant.