Anomalous Behaviors of Quantum Emitters in Non-Hermitian Baths

Abstract

Both non-Hermitian systems and the behaviour of emitters coupled to structured baths have been studied intensely in recent years. Here we study the interplay of these paradigmatic settings. In a series of examples, we show that a single quantum emitter coupled to a non-Hermitian bath displays a number of unconventional behaviours, many without Hermitian counterpart. We first consider a unidirectional hopping lattice whose complex dispersion forms a loop. We identify peculiar bound states inside the loop as a manifestation of the non-Hermitian skin effect. In the same setting, emitted photons may display spatial amplification markedly distinct from free propagation, which can be understood with the help of the generalized Brillouin zone. We then consider a nearest-neighbor lattice with alternating loss. We find that the long-time emitter decay always follows a power law, which is usually invisible for Hermitian baths. Our work points toward a rich landscape of anomalous quantum emitter dynamics induced by non-Hermitian baths.

Bound states and photon emission in non-Hermitian nanophotonics

“…III, we present the first case study on the general Hatano-Nelson model, extending the unidirectional limit considered in Ref. [75]. This example showcases the impact of NH topology.…”

“…In particular, we provide quantitative explanations to the algebraic atom decays observed in Ref. [75]. In Sec.…”

“…As already highlighted in Ref. [75], the NH skin effect results in the so-called "hidden" bound states that behave very differently from the usual bound states in Hermitian systems. For example, they have the remarkable property that their energy is exactly pinned to the emitter detuning.…”

“…In the companion letter [75], we obtained the analytic expression for the time evolution of a photon emitted from the atomic excitation in the unidirectional limit. While it seems impossible to have an analytic solution in the general case, we can readily perform numerical calculations.…”

“…In particular, we provide further detail on the passive P Tsymmetric lattice studied in Ref. [75] and quantitatively explain the exponents of algebraic decay. We also provide a few more examples exhibiting non-exponential decay in both 1D and 2D.…”