报告题目: 二维机械谐振器与超导微波腔的耦合
报告 人: Johannes Guettinger 教授德国亚琛工业大学（RWTH Aachen University） JARA-FIT 和第二物理研究所的助理教授。
报告时间: 2016年8月1日（周一）14:00
报告地点：物理科技楼101
报告人简介：2012年Johannes Guettinger 教授在瑞士苏黎世联邦工学院取得博士学位，研究方向是石墨烯量子点的输运特性，在攻读博士学位的4年期间发表了30多篇高影响因子论文。2012-2015年他在西班牙光子学研究所做博士后研究员，期间开发和研究了石墨烯机械谐振器与超导腔间的耦合工作。2016年，他在德国亚琛工业大学获得助理教授职位，主要研究方向是石墨烯机械谐振器的相关应用。如有兴趣与他联系，可以发送电子邮件到guettinger@physik.rwth-aachen.de。
报告摘要: Lightweight mechanical resonators have been used with great success to investigate motion in the quantum regime, probe rich nonlinear phenomena, and sense minuscule masses and forces. In this context, we study the motion of graphene and other 2D mechanical resonators by capacitive coupling of the membrane to a superconducting microwave cavity1-3. The high sensitivity of this microwave-mechanical readout allows us to detect the motion with femtometer precision. The combination of the high readout sensitivity with the low mass enables the demonstration of a force sensitivity in the zeptonewton regime which is promising for detecting single electron and nuclear spins. The strong coupling to the cavity enables cooling of the mechanical motion towards the quantum ground state. In order to improve the cooling rate, we make use of the strong electrostatic tunability of the molecular membrane. Thereby, we demonstrate sideband cooling of the mechanical motion to 7.2 quanta of vibration. The high sensitivity readout allows us also to investigate time resolved mechanical motion in graphene mechanical resonators. We observe surprising discontinuities in the decay from elevated mechanical energies, which indicate the presence of energy dependent decay channels. We attribute this behavior to nonlinear decay processes, such as the scattering of multiple quanta of vibrations of the fundamental mode into one quantum of a higher energy eigenmode. At low excitation energies we measure record long mechanical lifetimes in graphene resonators with quality factors surpassing 1 million. These findings offer new opportunities for manipulating vibrational states and show promise for investigating the motion of atomically-thin resonators in the quantum regime.