# Séminaire du LPTMS: Pierre-Elie Larré & Clément Tauber

## Quantum simulating many-body phenomena with propagating light

### Pierre-Elie Larré (Université de Cergy-Pontoise)

We consider the propagation of a quantum light field in a cavityless nonlinear dielectric. In this all-optical platform, the space propagation of the field’s envelope may be mapped onto the time evolution of a quantum fluid of interacting photons. The resulting many-body quantum system constitutes a particular class of quantum fluids of light and presently attracts a growing interest as a powerflul tool for quantum simulation. I will present recent theoretical and experimental progresses in this rapidly emerging research field, including investigations on superfluidity, elementary excitations, disorder, quantum quenches, prethermalization, thermalization, and Bose-Einstein condensation.

## Bulk-edge correspondence for Floquet topological insulators

### Clément Tauber (ETH, Zürich)

Floquet topological insulators describe independent electrons on a lattice driven out of equilibrium by a time-periodic Hamiltonian, beyond the usual adiabatic approximation. In dimension two such systems are characterized by integer-valued topological indices associated to the unitary propagator, alternatively in the bulk or at the edge of a sample. In this talk I will give new definitions of the two indices, relying neither on translation invariance nor on averaging, and show that they are equal. In particular weak disorder and defects are intrinsically taken into account. Finally indices can be defined when two driven sample are placed next to one another either in space or in time, and then shown to be equal. The edge index is interpreted as a quantized pumping occurring at the interface with an effective vacuum.

**Date/Time : ** 23/01/2018 - *11:00 - 12:00*

**Location : ** LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay

#### Upcoming seminars

- Physics-Biology interface seminar: David Bensimon - 30 Mai 2018 - 11:00
- Physics-Biology interface seminar: Karim Benzerara - 13 Juin 2018 - 11:00
- Physics-Biology interface seminar: Knut Drescher - 27 Juin 2018 - 11:00