TOPOGRAND · Non-Hermitian Topological Physics in Grand Canonical Photon Lattices

Topology is a powerful paradigm for the classification of phases of matter. One of its direct manifestations in the widely studied Hermitian systems, which are isolated from the environment, are robust states that emerge at the interfaces between matter with distinct topological order. Real systems, however, are never truly isolated from their surroundings and the influence of the environment on the topologically protected states remains to a large extent unknown. Even more importantly, understanding and controlling the openness of non-Hermitian systems can provide fundamentally new ways to create novel topological states of matter. TopoGrand will realise a new experimental platform to synthesise non-Hermitian topological materials. It will employ a room-temperature photonic platform combining nanostructured optical microcavities with a molecular medium, to achieve non-Hermitian topological lattices of photon condensates. The system will feature tuneable openness that is unique among other presently available experimental platforms: a controlled flux of excitations via spatially selective pumping and loss, energy dissipation at variable rates, and coherence modified by grand canonical reservoirs. New physics will be accessed in the course of this work: TopoGrand will demonstrate genuine non-Hermitian topological phases and edge states without a Hermitian counterpart. Specifically, we will test the emergence of interface states at a topological phase boundary and their robustness against lattice disorder, as well as reservoir-induced fluctuations. The project presents a completely new approach to topology, which will allow us to create reconfigurable photonic materials with topological protection simply by controlling the environment. With the novel toolbox, I will explore the emerging links between photonics, condensed matter systems and quantum computing, and emulate finite-temperature topological systems, which are at the forefront of research in quantum physics.