Laboratory for Physical Sciences Seminar Announcement
Wednesday, October 13, 2010; 3:30 p.m.
Refreshments served at 3:00 p.m.
Seminar Room, Lower Level, LPS
8050 Greenmead Dr., College Park, MD 20740 301-935-6400
Title: Coherence of Donor Electron Spins in Isotopically Enriched Silicon
Wayne Witzel
Sandia National Labs
Silicon is promising for spin-based quantum computing because nuclear
spins, a source of magnetic noise, may be nearly eliminated through
enrichment. However, any Si device is expected to contain some
phosphorus donor impurities. These donors generate magnetic noise
through spin dynamics, induced by dipolar interactions, that conserve
Zeeman and hyperfine energies. Ironically, increasing the number of nuclear
spins will suppress this decoherence mechanism by effecting more hyperfine energy
variation (i.e., Overhauser shifts). We study spin coherence decay as a
function of donor concentration, $^{29}$Si concentration, and temperature using
cluster expansion techniques specifically adapted to the problem of a sparse
electron spin bath.