LPS Seminar: Oct 13 – Wayne Witzel

October 8th, 2010  |  Published in All, Upcoming Talks

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.

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