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Manipulation of Nuclear Spins in Semiconductor Nanostructures

Speaker:Dr. W. Yao
Affiliation:Department of Physics, The University of Hong Kong
Date:March 7, 2011
Time:5:00 - 6:30 p.m.
Venue:Lecture Theatre T4, Meng Wah Complex, HKU


Nuclear spin in semiconductor nanostructures has attracted extensive interests either as a deleterious noise source or as a superb information storage in quantum technology. Nuclear spins are completely random and of large fluctuations in thermal equilibrium at temperatures as low as tens of millikelvin. For electron spin qubit in III-V semiconductors, the inevitable lattice nuclear spins become the main course of qubit decoherence. In the meantime, because of the extremely weak coupling with environment, nuclear spin system is capable of ultra-long storage of quantum coherence and holds promise for room temperature quantum information processing. In this talk, I will give a brief overview on how electron spin qubit lose coherence by the fluctuations of nuclear spin environment. I will discuss preparation of nuclear spin environment using optical and electrical controlled dynamic nuclear polarization processes such that the electron spin coherence time can be substantially increased. I will also introduce a novel approach for squeezing nuclear spins into many-body singlets, which effectively removes these deleterious spin moments from the surrounding of the electron. This squeezing approach can also be developed into a scheme for engineering large scale pure-state entanglement and for initialization to decoherence free subspace in Kane quantum computing architecture using nuclear spin as qubit.


About the Speaker:

Dr. Yao received his BS degree from Peking University in 2001, and PhD degree from University of California at San Diego in 2006. From 2006 to 2008, he was a postdoctoral fellow in The University of Texas at Austin. He joined Department of Physics of HKU in 2008. His research interest lies in an interdisciplinary field across condensed matter physics, quantum physics, and optical physics.


Physics colloquium series is organized to introduce cutting edge researches and new development in physics, designed to be suitable to graduate and undergraduate students, and also to scientists working on different fields. Each colloquium will generally start with an extensive introduction of the background of the field, followed by forefront research topics and results. The colloquium will serve as an education forum for students and laymen alike, and also serve as a platform for exchange and update their knowledge of various branches of physics among academic staff members.