Frustration-induced anomalous transport and strong photon decay in waveguide QED

Ron Belyansky,Yidan Wang,Andrei Vrajitoarea,Rex Lundgren,Andrew A Houck,Seth Whitsitt,Alexey V Gorshkov

doi:10.1103/physrevresearch.3.l032058

Abstract

We study the propagation of photons in a one-dimensional environment consisting of two non-interacting species of photons frustratingly coupled to a single spin-1/2. The ultrastrong frustrated coupling leads to an extreme mixing of the light and matter degrees of freedom, resulting in the disintegration of the spin and a breakdown of the "dressed-spin", or polaron, description. Using a combination of numerical and analytical methods, we show that the elastic response becomes increasingly weak at the effective spin frequency, showing instead an increasingly strong and broadband response at higher energies. We also show that the photons can decay into multiple photons of smaller energies. The total probability of these inelastic processes can be as large as the total elastic scattering rate, or half of the total scattering rate, which is as large as it can be. The frustrated spin induces strong anisotropic photon-photon interactions that are dominated by inter-species interactions. Our results are relevant to state-of-the-art circuit and cavity quantum electrodynamics experiments.

Highlights

Photons propagating in one-dimensional environments are a fundamental building block for quantum optics and waveguide quantum electrodynamics (QED)
We find that inelastic processes, where the photon decays into several smaller-energies photons, can be as important or even dominate the elastic
As we show for intermediate coupling strengths α 0.4, R plays an important role in the photon dynamics, where it can be interpreted as the splitting of the dressed spin, whereas this picture breaks down for larger α

Summary

Introduction

Photons propagating in one-dimensional environments are a fundamental building block for quantum optics and waveguide quantum electrodynamics (QED). Using a combination of numerical and analytical methods, we show that the elastic response becomes increasingly weak at the effective spin frequency, showing instead an increasingly strong and broadband response at higher energies. We find that inelastic processes, where the photon decays into several smaller-energies photons, can be as important or even dominate the elastic

Results

Conclusion