Nonreciprocal routing induced by chirality in an atom-dimer waveguide-QED system

TL;DR

This paper proposes a quantum routing scheme using a waveguide-QED system with two coupled atoms and introduces chirality to control single-photon transmission, working in both Markovian and non-Markovian regimes.

Contribution

It provides an exact analytical model for single-photon routing in a chiral waveguide-QED system, demonstrating nonreciprocal control without requiring ideal chiral coupling.

Findings

Single-photon transmission can be controlled on demand in the non-Markovian regime.

Complete single-photon routing is achievable without ideal chiral coupling.

The system's behavior differs between Markovian and non-Markovian regimes.

Abstract

The implementation of quantum routers is an important and desired task in quantum information science, since quantum routers are important components of quantum networks. Here, we propose a scheme for implementing single-photon routers in a waveguide-QED system, which consists of two coupled two-level atoms coupled to two waveguides to form a four-port quantum device. We obtain the exact analytical expressions of the single-photon scattering amplitudes using the real-space method. By taking the propagating time of photons between two coupling points into account or not, we consider the system working in the Markovian and non-Markovian regimes, respectively. In addition, we introduce the chiral coupling, which breaks the symmetry of the waveguide model, to manipulate the transmission of single photons. We find that when the system works in the non-Markovian regime, the single photon can be transmitted on demand by adjusting the asymmetry coefficient. More interestingly, the complete single-photon routing in this device does not require an ideal chiral coupling, loosening the photon transport conditions. This work will motivate the studies concerning the nonreciprocal and chiral quantum devices in the waveguide-QED platform.