Collège de France

Jean Dalibard

Chaire Atomes et Rayonnement

Année 2023-2024

Séminaire - Guido Pupillo : Semilocalization of Disordered Spins in Cavity QED

Guido Pupillo

Université de Strasbourg et Centre Européen de Sciences Quantiques, ISIS (U. Strasbourg et CNRS)

Résumé

Light-matter interactions are playing an increasingly crucial role in the understanding and engineering of new states of matter with relevance to the fields of quantum optics, solid state physics, chemistry and materials science. Experiments have shown that significant modifications of material properties and transport can occur in a cavity in the regime of collective strong light-matter coupling even without external irradiation—"in the dark". In this colloquium-style talk we focus on disorder—a key feature of many materials—, in particular on general models for disordered spins coupled to the photon field of a cavity. We show that collective light matter interactions can dramatically alter the many-particle spin wavefunctions even in the limit of vanishingly small photon numbers: Subtle, permanent changes in the wavefunctions result from the combined effects of vacuum hybridization and long-range cavity-mediated couplings between the spins. A surprising, general, result is the realization of "semilocalization", a famous and elusive effect in quantum physics, usually associated to critical states of Anderson-like transitions. We discuss implications for energy transport and novel quantum phases mediated by long-range couplings in molecular physics and quantum optical systems.

Guido Pupillo

Guido Pupillo is Distinguished Professor at the University of Strasbourg and Director of the Centre Européen de Sciences Quantiques (CESQ) at the Institut de Science et d'Ingénierie Supramoléculaires (ISIS) of the University of Strasbourg and CNRS, where he is involved in the development of teaching and research programs in quantum science and technology. He obtained a Master in Theoretical Physics at the University of Bologna (IT) and a PhD in Physics in 2005 at the University of Maryland for research conducted at the National Institute of Standards and Technology (US). Until 2011 he was scientist and then senior scientist at the University of Innsbruck and the Austrian Academy of Sciences (AT), where he obtained the Habilitation in Theoretical Physics. Since 2012 he is full professor at the University of Strasbourg. He is recipient of several fellowships and awards, including the 2012 ERC Starting Grant, the 2013 Guy Ourisson Prize and the 2019 senior fellowship of the Institut Universitaire de France (IUF). His research interests are in atomic, molecular, and optical physics, quantum simulations and quantum computing.