学术报告会

时间：2019年6月18日     上午9：00

地点：理六301

报告人：温建明   美国肯尼索州立大学助理教授

Extending Weak Measurement to a non-Hermitian Hamiltonian

-- Probing sub-Hertz resonance spectroscopy

Jianming Wen^1,2,3

¹Department of Physics, Kennesaw State University

²Department of Physics, Emory University

³Department of Physics & Astronomy, Georgia State University

ABSTRACT

Being a hallmark of quantum mechanics, measurement assumes a very fundamental role since the very act of measuring a system is irrevocably accompanied by a complementary disturbance. Contrary to standard projective measurement prototypically modeled by von Neumann, the notion of weak measurements (WMs) introduced by Aharonov, Albert, and Vaidman describes an intriguing situation where partial information is gained by feebly probing the system without undermining its initial state through pre- and post-selection. Although the the uncertainty in each measurement is large because of the weak perturbative nature of the information extraction, this can be generally overcome by averaging over a vast number of identically prepared states. What makes WM an interesting phenomenon is that by post-selecting the prepared system, the weak value (WV) of an observable can lie well outside of the normal range of eigenvalues of the measurement operator, or even become complex owing to nontrivial interference of complex amplitudes. These peculiar features prove to be powerful for deeper understanding of quantum paradoxes, addressing important questions on the foundations of quantum mechanics, and triggering various metrological applications by alleviating technical imperfections. In this talk, after overviewing the essential concepts and procedures associated with WM, I will introduce our recent work [1] on employing this measurement to narrow the g⁽²⁾(0)-resonance linewidth down to sub-Hertz level and achieve the sensitivity of sensing weak magnetic field near DC just above the photon-shot-noise limit for a noise-fluctuation correlated system [2]. Different from previous WM results, our work exhibits a number of unique features. These include that the purely imaginary Hamiltonian describing the interaction between the system operator and the measurement device operator; the unusual frequency system operator; and the Stokesσz

References:

[1]  W. Qu, J. Sun, S. Jin, L. Jiang, J. Wen, and Y. Xiao, arXiv: 1812.02551.

[2]  L. Feng, P. Li, L. Jiang, J. Wen and Y. Xiao, Phys. Rev. Lett. 109, 233006 (2012).

BIOGRAPHY

Jianming Wen, an assistant professor in the Physics Department at Kennesaw State University. He also holds Adjunct Assistant Professor positions in the Department of Physics at Emory University and Department of Physics & Astronomy at Georgia State University. Prior to the current appointment, he was an Associate Research Scientist in the Applied Physics Department and Yale Quantum Institute at Yale University from 2013 to 2017. He has published 38 peer-reviewed journals in Nature Physics, Nature Photonics, Nature Communications, PRL, Advances in Optics and Photonics and others. His research interests lie in the interface of fundamental physics and technologies, including AMO physics, photonics, optical imaging, condensed matter physics, and quantum technologies. He serves as an active reviewer for over 40 major journals published by APS, OSA, IOP, Wiley, Springer, AIP, Elsevier, IEEE, Royal Society, and Nature. He also serves as an external reviewer for grant proposals submitted to French National Research Agency, Italian Ministry of Education, Universities and Research, Research Grants Council of Hong Kong, etc. In 2015 he received the OSA Outstanding Reviewer Award; in 2018 and 2019, also received the IOP Outstanding Reviewer Award. He obtained his Ph.D. in physics, in a cornerstone group on quantum optics, from the University of Maryland Baltimore County and his B.S. in Physics from Shandong University in the mainland in 2001. His research is currently supported by NSF and KSU.