# Phase controlled single-photon nonreciprocal transmission in a one-dimensional waveguide

## TL;DR

This paper demonstrates phase-controlled, nonreciprocal single-photon transmission in a one-dimensional waveguide coupled to a three-level system, with potential for experimental realization using current technologies.

## Contribution

It introduces a novel scheme for achieving controllable nonreciprocal photon transmission using phase-sensitive coupling in a waveguide-emitter-cavity system.

## Key findings

- Achieves perfect transmission via quasidark states when emitter and cavity are co-located.
- Realizes robust, controllable nonreciprocal transmission with spatially separated emitter and cavity.
- Shows the proposed system is feasible with existing experimental setups.

## Abstract

We study the controllable single-photon scattering via a one-dimensional waveguide which is coupled to a two-level emitter and a single-mode cavity simultaneously. The emitter and the cavity are also coupled to each other and form a three-level system with cyclic transitions within the zero- and single-excitation subspaces. As a result, the phase of emitter-cavity coupling strength serves as a sensitive control parameter. When the emitter and cavity locate at the same point of the waveguide, we demonstrate the Rabi splitting and quasidark-state--induced perfect transmission for the incident photons. More interestingly, when they locate at different points of the waveguide, a controllable nonreciprocal transmission can be realized and the non-reciprocity is robust to the weak coupling between the system and environment. Furthermore, we demonstrate that our theoretical model is experimentally feasible with currently available technologies.