时间：11月23日（周四）早上10:00-11:00

地点：D楼204

报告人：Prof. Gerd Schön，Karlsruhe Institute of Technology, Germany

摘要：

Progress with microfabricated quantum devices has revealed that an ubiquitous source of noise are parasitic two-level systems (TLSs). For superconducting qubits, TLSs residing on electrode surfaces and in tunnel junctions account for a major part of decoherence and thus pose a serious roadblock to the realization of solid-state quantum processors. Recent experiments [J. Lisenfeld et al., Sci. Rep. 6, 23786 (2016)] utilized a superconducting qubit to explore the quantum state evolution of these material-based TLSs in order to shed new light on their individual properties and environmental interactions.

We studied theoretically the dephasing of these individual high-frequency TLSs due to their interaction with an ensemble of low-frequency thermal TLSs which are described by the standard tunneling model (STM). We show that the dephasing by the bath of TLSs explains both the dependence of the Ramsey dephasing rate on an externally applied strain as well as its order of magnitude, as observed in experiment.

专家简介：http://www.tfp.kit.edu/265.php

1991 – present, University of Karlsruhe, Full Professor of Physics,   chair: Institut für Theoretische Festkörperphysik；1998 – present, Group Leader at the Forschungszentrum Karlsruhe, Institute of Nanotechnology 。共发表文章200多篇;其中13篇是Reviews, Book Chapters (包括一篇Rev. Mod. Phys. (2001)) ; 多篇Nature文章,几十篇PRL;其余几乎都是PRB类似的文章。