Exotic interactions mediated by a non-Hermitian photonic bath

Abstract

We study the exotic interaction between emitters mediated by the photonic modes of a lossy photonic lattice described by a non-Hermitian Hamiltonian. We show in a paradigmatic case study that structured losses in the field can seed exotic emission properties. Photons can mediate dissipative, fully non-reciprocal, interactions between the emitters with range critically dependent on the loss rate. When this loss rate corresponds to a bare-lattice exceptional point, the effective couplings are exactly nearest-neighbour, implementing a dissipative, fully non-reciprocal, Hatano-Nelson model. Counter-intuitively, this occurs irrespective of the lattice boundary conditions. Thus photons can mediate an effective emitters' Hamiltonian which is translationally-invariant despite the fact that the field is not. We interpret these effects in terms of metastable atom-photon dressed states, which can be exactly localized on only two lattice cells or extended across the entire lattice.

Anomalous Behaviors of Quantum Emitters in Non-Hermitian Baths

“…It may also be interesting to explore the impact of higher-order [39] and higher-dimensional exceptional objects, such as exceptional rings [40] and surfaces [41], whose systematic constructions have become clear recently [42][43][44]. Last but not least, introducing non-Hermiticity to nanophotonic baths may significantly extend the freedom of engineering effective (bath-mediated) interactions between atoms [45].…”

Bound states and photon emission in non-Hermitian nanophotonics

“…While there are a few previous studies about this topic (see, e.g., Refs. [68,69]), all of them focus on rather specific (classes of) models. Moreover, the role of genuine NH topology [31,34,35] remains fully unexplored.…”

Non-Hermitian physics and master equations

“…Finally, we briefly mention that such a non-Hermitian photonic structure can yield exotic phenomena in a waveguide QED setup, as discussed in Ref. [42]. Remarkably, by weakly coupling emitters such as two-level atoms or resonators to an array of coupled cavities with patterned local dissipation, it turns out that the non-Hermitian lattice can mediate second-order (dissipative) interactions between the emitters with unique properties which are unusual if not unachievable in Hermitian baths.…”

“…For instance, at the EP of the photonic structure in Ref. [42], the interaction between emitters (in the weakcoupling and Markovian regime) is described by an effective non-Hermitian Hamiltonian of the form…”

“…with Γ a rate that is quadratic in the emitter-cavity couping strength [42]. This represents an implementation of the (dissipative) fully non-reciprocal Hatano-Nelson model, cf.…”