Memory effects in disordered matter – granular suspensions, ferromagnets, crumpled paper…– can be described as pathways between the different states visited by the system upon driving. However, due to their complexity, we lack strategy to experimentally probe, understand and control such pathways in most memory forming systems.

We introduce mechanical driving of corrugated elastic sheets to precisely observe and manipulate complex, multi-step pathways. These systems respond to simple 1D forcing via sequences of elastic snap-through instabilities, leading to complex– yet controlled–deformation pathways, reminiscent of memory effects. In particular we use manipulations of the boundaries to elicit a multitude of pathways from a single sample, and show how interactions between the instabilities lead to new pathways, akin to information processing.

An analog simulator is a synthetic physical system, which emulates in a controlled way a physical problem. You can get answers about the physical problem by directly performing experiments on the simulator. In the present seminar, I will present the polariton platform and explain how it is relevant for analog simulation of many interesting complex problems.
Cavity polaritons are hybrid exciton-photon quasi-particle emerging from the strong coupling regime between photons confined in an optical cavity and excitons confined in quantum wells. They present physical properties reflecting their mixed nature. From the photon part, they inherit a small effective mass and can be confined in lattices with typical dimensions of the order of a few microns. Their excitonic part endows them with inter-particle interactions resulting in a giant Kerr non linearity. Moreover the system is intrinsically open and out of equilibrium because photons constantly leak out from the cavity. Cavity polaritons have been shown to present fascinating properties such as Bose Einstein condensation at elevated temperature, superfluidity, multistability etc [1].
In the present talk, I will explain how the polariton plateform is particularly suitable to realize analog simulation of open complex systems and explore fundamental physical phenomena.
I will describe a few recent results of our group:
1) How do wave localize in exotic quasi-crystals and how fractality does develop? This physics can be emulated with polariton lattices [2]
2) Polariton condensates are out of equilibrium and their phase dynamics has been predicted to obey the celebrated Kardar Parisi Zhang (KPZ) equation. We have been able to reveal experimentally universal KPZ scaling laws in the first order coherence of a 1D polariton condensate.[3]
3) Polariton lattices are also very interesting for the investigation of topological photonics. In particular, the ability to drive the system with controlled phases opens a new paradigm for non-linear topological photonics. [4]

References :

[1] C. Ciuti & I. Carusotto, Quantum fluids of light, Rev. Mod. Phys. 85, 299 (2013)
[2] V. Goblot et al. Emergence of criticality through a cascade of delocalization transitions in quasiperiodic chains, Nature Physics 16, 832 (2020)
[3] Q. Fontaine et al., Observation of KPZ universal scaling in a one-dimensional polariton condensate, arXiv:2112.09550 (2021)
[4] N. Pernet et al., Topological gap solitons in a 1D non-Hermitian lattice, arXiv:2101.01038 (to appear 2022)