Prof. Eugene Demler Theory Lectures

Prof. Eugene Demler’s Bio

Eugene Demler received a PhD in theoretical physics from Stanford University in 1998. He was a Junior Fellow in the Harvard Society of Fellows, became an assistant professor at Harvard in 2001 and a full professor there in 2005. In the Fall of 2021, he moved to ETH Zurich, Switzerland, as a full professor. In 2015, he was the winner of a Humboldt Research Award and became a Distinguished Scholar at the Max Planck Institute for Quantum Optics in Munich, Germany. In 2021 he received the Hamburg Prize for Theoretical Physics. His research focuses on understanding strongly correlated quantum systems, from electrons in solids to dilute atomic gases to photons. His work covers diverse areas, such as magnetism and superconductivity, many-body physics with ultracold atoms in optical lattices, nonlinear quantum optics, understanding light induced states of matter, and developing real world applications of NISQ devices.

Scheduled talks

Lecture I

Monday, January 9, 11-13, SMR

Waveguide quantum electrodynamics with many-body electron system

Abstract

In this talk, I will discuss the applications of cavity electrodynamics for controlling many-body electron systems. The focus will be on achieving strong coupling between cavities and collective excitations of interacting electrons at Terahertz and IR frequencies. As a specific example I will consider a cavity platform based on a two dimensional electronic material encapsulated by a planar cavity consisting of ultrathin polar van der Waals crystals. I will also discuss how metallic mirrors sandwiching a paraelectric material can modify the transition into the ferroelectric state. Finally, I will review a general question of theoretically describing ultrastrong coupling waveguide QED. I will present a novel approach to this problem based on a non-perturbative unitary transformation that entangles photons and matter excitations. In this new frame of reference, the factorization between light and matter becomes exact for infinite interaction strength and an accurate effective model can be derived for all interaction strengths.

Lecture II

Tuesday, January 10, 10-12, BLR

Optical responses of photoexcited materials: from parametric amplification to photoinduced superconductivity

Abstract

Optical drives at terahertz and mid-infrared frequencies in quantum materials are commonly used to explore nonlinear dynamics of interacting many-body systems. Recent experiments have demonstrated several surprising optical properties of transient states induced by driving, including the appearance of photo-induced edges in the reflectivity, enhancement of reflectivity, and even light amplification. I will show that many of these unusual properties can be understood from the general perspective of reflectivity from Floquet materials, in which pump-induced oscillations of a collective mode lead to parametric generation of excitation pairs. This analysis predicts a universal phase diagram of drive induced features in reflectivity, which evidence a competition between driving and dissipation. I will argue that this mechanism explains several recent experimental observations, including photoinduced superconductivity in the pseudogap phase of high Tc cuprates.

Lecture III

Wednesday, January 11, 10-12, BLR

Quantum simulators: from the Fermi Hubbard model to quantum assisted NMR inference

Abstract

I will discuss recent progress of optical lattice emulators of the Fermi Hubbard model, specifically the new availability of snapshots of many-body states with single particle resolution. I will review new insights from these experiments on the properties of doped Mott insulators, including the demonstration of magnetically mediated pairing. I will also present the idea of using quantum simulators to perform inference of NMR spectra for biological molecules. I will review a recent experimental realization of this algorithm on a quantum computer using trapped ions. Prospects for scaling this approach to solving practically relevant problems will be discussed.

Lecture IV

Thursday, January 12, 10-12, SMR

Single-spin qubit magnetic spectroscopy of the correlated states of electrons

Abstract

A single-spin qubit placed near the surface of a material acquires an additional contribution to its relaxation rate due to magnetic noise created by the low energy excitations of the electron system. I will discuss how this noise can be used to investigate different types of electronic states, including superconductors, , ferro- and antiferromagnetic insulators, and spin liquid states.