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Events on Thursday, May 2nd, 2013

R. G. Herb Condensed Matter Seminar
Bulk Phononic Crystal as Quantum Information Bus between Shallow Donor Spins
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Vadim Smelyanskiy, NASA, Ames Research Center
Abstract: We propose a new candidate for a spin qubit based on shallow donor spins in the semiconductor with very low isotopic concentration of nuclear spins and with spin orbital interaction many orders of magnitude stronger than that in silicon. In a uniform material this interaction leads to a short spin lifetimes. However we show that this lifetime increases dramatically when donor spin is placed in quasi-2D bulk phononic crystal (PnC) with the energy of a Zeeman splitting being inside of a complete phononic bandgap. In this situation single phonon processes are suppressed by energy conservations. We show that two-phonon decay remains very slow while virtual phonon exchange leads to a strong coupling between donor spins. We show that resonance coherent excitation transfer between the spins is enhanced exponentially when their Zeeman splitting is tuned near the phononic crystal band edge. We also show that long-range longitudinal interaction (z-z) between spins in PnC is very similar to then one mediated by Lamb waves in elastic plate. We explore various PnC cell shapes and proportions to maximize the above coherent effects and minimize the decay rate, focusing mainly on the quasi-2D square "Cross" crystal type initially proposed by Safavi-Naeini and Painter. We show that the system is a very interesting candidate for the quantum computing applications with unit cell size ~ 100-150nm.
Host: Coppersmith & Saffman
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