Princeton University

School of Engineering & Applied Science

Using noise spectroscopy to infer dynamics of quantum many-body systems

Speaker: 
Kartiek Agarwal, Harvard University
Location: 
E-Quad B205
Date/Time: 
Friday, January 22, 2016 - 11:00am

Abstract: 'Noise' is traditionally understood to be something of a nuisance: it leads to irregularities in the way our machines work, and it delays our ascendancy into the age of quantum computers. But noise is also an intrinsic property of real systems, and by fluctuation-dissipation relations, it is tied to many useful linear-response properties of the system. The main aim of this talk is to highlight how spatially/frequency-resolved measurements of noise can non-invasively determine the complete form of the conductivity and polarizability of the underlying quantum system, thus, largely characterizing the dynamics of the system. I will focus on two cases:
(1) Strongly disordered Heisenberg spin-networks. Using a novel real-space RG method to calculate magnetic noise, we show that these systems, under certain conditions, emit 1/f α noise, which is tied to both anomalous diffusion and many-body-localization in the system.
(2) Intrinsic/Doped graphene and 2DEGs. I discuss how distance-dependence of electro-magnetic noise above a 2d sample exhibits a different functional form depending on whether the transport is ballistic or diffusive and probe criticality of wave-functions near mobility edges.
Biography: Kartiek Agarwal is a Ph.D. student in the Department of Physics at Harvard University, working in the group of Professor Eugene Demler.