A spin is a tiny quantum magnet that can be in a superposition of up and down states. It can serve as an information unit called qubit in quantum information processing. By unavoidable coupling to environments, however, a spin will lose it quantum coherence by decoherence. In this talk, I will show how the spin decoherence can be understood in quantum meachnics and how the environments can be effectively decoupled by frequently flipping the spin up and down. When the decoherence is under such dynamical decoupling control, we observed anomalous effects of quantum fluctuations. The spin under control becomes a sensitive probe of weak quantum noises from the environments, which is useful not only in ultrasensitive magnetometry such as single-molecule nuclear magnetic resonance but also in research of fundamental physics such as quantum criticality.
个人简介：
Professor Liu specializes in the research of quantum physics and condensed matters. He graduated from the Department of Physics, Nanjing University in1995, and received his PhD from the Institute of Semiconductors, Chinese Academy of Sciences in 2000. He then joined
Tsinghua Universityand the University of California, San Diegoas a postdoctoral fellow. In 2005, he joined CUHK and is now an Associate
Professor in the Department of Physics and Director of Centre for Quantum Coherence. He is currently the Vice President of the Physical
Society of Hong Kong. Professor Liu has published more than 50 papers in various peer-reviewed international journals including Nature,
Nature Nanotechnology, and Physical Review Letters and presented tens of invited talks in international conferences.He is a recipient of the
Young Researcher Award 2010 of CUHK.