Reflection by two level system: phase singularities on the Poincar\'e hypersphere

TL;DR

This paper explores how the phase and amplitude of light reflected by a two-level system in a waveguide can be controlled via the dipole's properties, revealing complex phase singularities on the Poincaré hypersphere.

Contribution

It introduces a phase singularity perspective to the reflection process, expanding understanding of light-matter interactions in 1D quantum systems.

Findings

Control of dipole affects phase and amplitude of scattered light

Reveals phase singularities on the Poincaré hypersphere

Enhances understanding of 1D emitter chains

Abstract

We consider the reflection of a photon by a two-level system in a quasi-one-dimensional waveguide. This is important in part because it forms the backdrop for more complicated proposals where many emitters are coupled to the waveguide: leading to super and subradiant coupling even when the emitters are distant. The incorporation of chiral effects, for example unidirectional emission of dipole emitters, has already led to rich physics such as dimer coupling. However, chirality is not the only effect of the dipole, as we explore from a phase singularity perspective. We demonstrate that control of the dipole allows a rich variety of control of the phase and amplitude of the scattered light in both directions. This expands the scope for the physics of 1D chains of emitters.