Mike Thewalt: The remarkable optical properties of highly enriched 28Si – new tools and approaches for silicon-based quantum information research

Friday, November 12, 2010 1:30 pm - 2:30 pm EST (GMT -05:00)

Mike Thewalt, Simon Fraser University

Most schemes for implementing quantum computing using a silicon-based technology already envision the use of enriched 28Si, since the elimination of the nuclear spin of the 29Si provides a completely spin-free host into which impurity electronic and nuclear spins, which are to be used as qubits, can be placed. This results in greatly increased coherence times for these spins – both the electron and nuclear T2 for the shallow donor 31P, one of the main qubit candidates, have recently been shown to exceed one second in highly enriched 28Si. However, we discovered in 2001 another quite unexpected property of enriched 28Si, namely, that the linewidths of a wide variety of optical transitions are more than an order of magnitude narrower than the already very sharp transitions in natural Si. This has lead to the development of new optical methods for the measurement of both the electronic and nuclear spins of 31P in 28Si, and for the optical hyperpolarization of both spin systems. I will show how this enables a novel optical NMR measurement of dilute 31P in a regime inaccessible to conventional NMR. I will discuss briefly several proposals for the measurement of the electronic and nuclear spins of a single 31P using these optical methods, as well as new results for the shallow donor 209Bi, which has a rich hyperfine structure due to the large I = 9/2 nuclear spin.