December 2023

Abstracts of the Quantum Center Lunch Seminar

Date: Thursday, December 7, 2023
Place: ETH Zurich, Hönggerberg, HPF G 6
Time: 12:00 - 13:30

Fermi Polarons under Strong Driving in Uniform Potentials

Franklin Vivanco - Experimental Quantum Engineering (Xu group), ETH Zurich

Ultracold Fermi gases provide an exceptional platform for investigating many-body phenomena due to their unique time and energy scales that are unattainable in solid-state systems. When impurities interact with a Fermi sea, they form quasiparticles known as Fermi polarons, which determine the quantum system's properties. By using a uniform Fermi gas and fast radio-frequency techniques, we explore Fermi polarons under varying drive strengths, ranging from weak to ultrastrong. By employing two distinct internal states of the impurity species, we establish a novel steady-state spectroscopy technique to extract the energy of the driven polaron. Additionally, we measure the decay rate and quasiparticle residue of the driven polaron by analyzing the Rabi oscillations between the two internal states. Remarkably, the extracted quasiparticle residue surpasses unity at large drive strengths, posing intriguing questions regarding the connection between Rabi oscillations and the impurity's spectral functions.

Exploring the dynamics of a Duffing resonator under two-tone drive

Letizia Catalini - Spin Physics and Imaging (Degen group), ETH Zurich

In the last decades, a combination of practical needs and fundamental questions brought a growing attention towards driven nonlinear resonators. For example, this nonlinearity can lead to interesting phenomena such as squeezing or detrimental performances where oscillators are desired to behavein linear way. One instance is in force sensing experiments where the nonlinearities limit the lowest achievable sensitivity. One typical way of investigating the nonlinear dynamics of a resonators consists of having a large pump drive and measuring the system's response to an additional weak probe drive. This approach has allowed researchers to characterize optical as well as nanomechanical systems. In all these experiments, the probe amplitude is kept small enough to only explore linear perturbations of the system around the dominant dynamics driven by the pump tone.

In contrast, we investigate the response of a single Duffing resonator to a combination of two strong drivetones at different frequencies. We observe a deviation from the typical Duffing response, which leads to a non-hysteretic regime characterized by periodic loops in phase space. Our results provide an understanding of the simplest pump-pump experiment of a nonlinear system and lay the groundwork for future exploration of multi-tone-drive nonlinear networks. Moreover, the two-tone drive we proposed pave the way for observing new dynamics in nonlinear systems.