Quantum Fisher information as signature of superradiant quantum phase transition

主讲人 (Speaker): 金光日 教授

主讲人单位 (Speaker's Institute): 北京交通大学

时间 (Time): 星期四, 2017/04/13 - 15:30 to 17:00

地点 (Location): 珠海校区行政楼八层天琴引力物理研究中心大会议室

摘要 (Abstract):

The single-mode Dicke model is well known to undergo a quantum phase transition from the so-called normal phase to the superradiant phase (hereinafter called the ‘superradiant quantum phase transition’). Normally, quantum phase transitions can be identified by the critical behavior of quantities such as entanglement, quantum fluctuations, and fidelity. In this talk, we present out recent work about the quantum Fisher information (QFI) and its behavior of both the field mode and the atoms in the ground state of the Dicke Hamiltonian. For a finite but large number of atoms, we show that near the critical atom-field coupling, the QFI of the atomic and the field subsystems can surpass their classical limits, due to the appearance of nonclassical quadrature squeezing. As the coupling increases far beyond the critical point, each subsystem becomes a highly mixed state, which degrades the QFI and hence the ultimate phase sensitivity. In the thermodynamic limit, we present the analytical results of the QFI and their relationship with the reduced variances of the field mode and the atoms. For each subsystem, we find that there is a singularity in the derivative of the QFI at the critical point, a clear signature of the quantum criticality in the Dicke model.

主讲人简介 (Speaker's CV):

金光日，男，博士，北京交通大学教授，博士生导师。2002年7月毕业于中科院理论物理所， 获理学博士学位。2007年进入北京交通大学物理系，任教授、博士生导师。2009年入选北京 交通大学红果园“双百”人才计划，2011年入选教育部新世纪优秀人才支持计划。主要研究 量子光学与量子调控理论，特别是量子精密测量理论，在超冷原子气体自旋压缩和光量子态相 位测量领域做出诸多有特色的理论研究工作。在国内外学术刊物上共发表SCI论文30余篇，其 中2篇发表在Phys. Rev. Lett.上。 主要研究兴趣： 量子光学，量子结构与量子调控。