报告题目：超辐射量子相变及光和原子复合系统基态的量子Fisher信息

报 告 人：金光日 教授

报告时间：2017年3月21日(周二)下午15:00-16:30

报告地点：理科楼南501报告厅

摘要：

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.

报告人简介：

金光日，男，1973年生，北京交通大学教授、博士生导师。2002年毕业于中科院理论物理所，师从著名物理学家孙昌璞院士，获得理学博士学位。2007年至今在北京交通大学物理系工作，主要研究量子光学与量子信息，在超冷原子气体和光量子态自旋压缩及其相位估值方向上做出了有特色的研究工作。现主持国家自然科学基金重大研究计划项目1项，完成国家自然基金和省部级等科研项目8项，发表SCI论文30余篇，其中2篇发表在物理学知名刊物Phys. Rev. Lett.上。   欢迎广大师生参加！

                                                     物理电子工程学院

                                                     2017年3月20日