# Coherent and radiative couplings through 2D structured environments

## TL;DR

This paper investigates how two or more quantum units interact through 2D structured environments, analyzing coherence, radiation, directionality, and entanglement decay in finite and infinite lattices, with implications for quantum technologies.

## Contribution

It provides a comprehensive comparison of coherent and radiative interactions in 2D lattices, including finite-size effects, directionality disruption, and subradiant state configurations, advancing understanding of quantum emitter dynamics.

## Key findings

- Directionality linked to isofrequency manifolds can be disrupted.
- Finite lattices exhibit different mode scaling and van Hove singularities.
- Subradiant states are more prominent in finite lattices, with zero induced coherence in dark states.

## Abstract

We study coherent and radiative interactions induced among two or more quantum units, by coupling them to two-dimensional lattices acting as structured environments. This model can be representative of atoms trapped near photonic crystal slabs, trapped ions in Coulomb crystals or to surface acoustic waves on piezoelectric materials, cold atoms on state-dependent optical lattices, or even circuit QED architectures, to name a few. We compare coherent and radiative contributions for the isotropic and directional regimes of emission into the lattice, for infinite and finite lattices, highlighting their differences and existing pitfalls, e.g. related to long-time or large-lattice limits. We relate the phenomenon of directionality of emission with linear-shaped isofrequency manifolds in the dispersion relation, showing a simple way to disrupt it. For finite lattices, we study further details as the scaling of resonant number of lattice modes for the isotropic and directional regimes, and relate this behavior with known van Hove singularities in the infinite lattice limit. Further we export the understanding of emission dynamics with the decay of entanglement for two quantum, atomic or bosonic, units coupled to the 2D lattice. We analyze in some detail completely subradiant configurations of more than two atoms, which can occur in the finite lattice scenario, in contrast with the infinite lattice case. Finally we demonstrate that induced coherent interactions for dark states are zero for the finite lattice.