Controlled unidirectional reflectionlessness by coupling strength in a non-Hermitian waveguide quantum electrodynamics system

TL;DR

This paper demonstrates how to achieve unidirectional reflectionlessness and coherent perfect absorption in a waveguide QED system by tuning coupling strength and phase parameters, with potential applications in quantum photonic devices.

Contribution

It provides analytical expressions and conditions for unidirectional reflectionlessness in a non-Hermitian waveguide QED system, highlighting control via coupling strength and phase modulation.

Findings

Unidirectional reflectionlessness occurs at exceptional points.

Coherent perfect absorption is observed near exceptional points.

Analytical expressions for transmission and reflection are derived.

Abstract

Unidirectional reflectionlessness is investigated in a waveguide quantum electrodynamics system that consists of a cavity and a $\Lambda$-type three-level quantum dot coupled to a one-dimensional plasmonic waveguide. Analytical expressions of transmission and reflection coefficients are derived and discussed for both resonant and off-resonant couplings. By appropriately modulating the coupling strength, phase shift and Rabi frequency, unidirectional reflectionlessness is observed at the exceptional points. And unidirectional coherent perfect absorption is exhibited at the vicinity of exceptional point. These results might find applications in designing quantum devices of photons, such as optical switches and single-photon transistors.