Strongly correlated photon transport in waveguide QED with weakly coupled emitters

TL;DR

This paper demonstrates that strongly correlated photon transport can occur in waveguides with dense emitter ensembles, even at weak coupling, due to nonlinear interactions and loss effects, with potential experimental realization.

Contribution

It introduces a universal asymptotic model for photon correlations in waveguide QED with weakly coupled emitters, applicable to both chiral and non-chiral systems.

Findings

Strong photon correlations arise from nonlinearity and loss interactions.

Correlated photon states are more resistant to losses than uncorrelated ones.

Results hold for randomly placed emitters without chirality.

Abstract

We show that strongly correlated photon transport can be observed in waveguides containing optically dense ensembles of emitters. Remarkably, this occurs even for weak coupling efficiencies. Specifically, we compute the photon transport properties through a chirally coupled system of $N$ two-level systems driven by a weak coherent field, where each emitter can also scatter photons out of the waveguide. The photon correlations arise due to an interplay of nonlinearity and coupling to a loss reservoir, which creates a strong effective interaction between transmitted photons. The highly correlated photon states are less susceptible to losses than uncorrelated photons and have a power-law decay with $N$. This is described using a simple universal asymptotic solution governed by a single scaling parameter which describes photon bunching and power transmission. We show numerically that, for randomly placed emitters, these results hold even in systems without chirality. The effect can be observed in existing tapered fiber setups with trapped atoms.