Chirale Vielteilchen-Quantenoptik in nano-strukturierten Umgebungen

01/06/2021 to 31/05/2024

An excited atom interacting with the radiation field decays by emitting a photon. This behaviour drastically changes in the case of an ensemble of atoms, as the emitters couple collectively to the radiation field: on one hand, the exchange of virtual photons induces dipole-dipole long-ranged interactions among the atoms. On the other hand, excitations in the ensemble can either decay extremely fast or remain stable over very long times due to constructive or destructive interference of the decay channels, respectively. These collective phenomena, that were theoretically predicted for atoms in free space already in the 1950s, have only rather recently been unambiguously demonstrated in several experiments.

Even richer physics can be observed when the atoms couple collectively to photonic nanostructures, such as photonic crystals and optical nanofibers. These systems support a small number of so-called guided electromagnetic modes, such that light propagates only longitudinally along the nanostructure. Selecting appropriately the positions and dipole polarizations of a nearby ensemble of atoms can open a photon decay channel into this small set of modes, which enables the transport of the light in the optical regime with negligible losses, while inducing all-to-all interactions among the atoms. These features have led to the identification of experimental platforms such as nanofibers, photonic crystals or photonic topological insulators coupled to nearby emitters, as candidate systems for the implementation of quantum information and communication protocols.

In this proposal, we will study a laser-driven ensemble of atoms coupled to the radiation field in the presence of these guiding photonic structures. The specific goals of our research are:

- to develop strategies for enhancing the coupling of the emitters to the guided modes of the nanophotonic structures, i.e. reducing the number of photons that are lost into free space. This will be essential to realize actual applications in quantum information and communications, such as non-reciprocal photonic devices or quantum state transport.

- to investigate the largely unexplored regime of strong laser driving, where the interplay between the driving and the all-to-all interactions will highlight a path towards the creation and exploration of strongly correlated atomic states.

- to elaborate a framework for the creation and analysis of guided photonic states. This will inform the development of steady-state sources of correlated photons and non-classical photonic states, with potential applications in quantum information and communication.

A detailed study of these photonic systems will not only allow to uncover and characterise new collective many-body phenomena but will almost certainly add new capabilities to these platforms which may be exploitable in future technological applications.