Abstract: An electron spin localized in a semiconductor is coupled by contact hyperfine interaction to the nuclei of the atoms of the host material. This coupling is the main reason for decoherence of semiconductor-based spin qubits. Describing the process of decoherence is an interesting problem, because the experimentally relevant parameter regime corresponds to strong qubit-bath coupling, and the bath dynamics is very slow. Both of these features preclude the use of Born-Markov approximation commonly used for description of open quantum systems. I will try to give a survey of theoretical methods which were used (with varying degree of success) to attack this problem during the last 10 years.

About the Speaker: Lukasz Cywinski got his masters degree at the Faculty of Physics of Warsaw University in Poland. He did his graduate thesis under the supervision of professor Lu Jeu Sham, and obtained the PhD title in 2007, after which he worked as a postdoctoral researcher for Professor Sankar Das Sarma in the Condensed Matter Theory Center, University of Maryland at College Park. Since 2009 he is an assistant professor in the group of Professor Tomasz Dietl at the Institute of Physics, Polish Academy of Sciences. He has worked on spin qubit decoherence, spintronics, ultrafast magnetization dynamics, and topological insulators based on narrow-gap semiconductors.