Collective radiation from distant emitters

TL;DR

This paper investigates how finite light speed affects the radiation properties of distant quantum emitters coupled via waveguides, revealing non-Markovian spectral features and a distance-dependent dipole interaction decay.

Contribution

It introduces a toy model analyzing non-Markovian effects on radiated fields from distant emitters, highlighting linewidth broadening, Fano resonances, and exponential decay of interactions due to retardation.

Findings

Spectral linewidth broadening beyond superradiance observed.

Fano resonance-like peaks identified in the radiated spectrum.

Dipole-dipole interaction decays exponentially with distance.

Abstract

Waveguides allow for direct coupling of emitters separated by large distances, offering a path to connect remote quantum systems. However, when facing the distances needed for practical applications, retardation effects due to the finite speed of light are often overlooked. Previous works studied the non-Markovian dynamics of emitters with retardation, but the properties of the radiated field remain mostly unexplored. By considering a toy model of two distant two-level atoms coupled through a waveguide, we observe that the spectrum of the radiated field exhibits non-Markovian features such as linewidth broadening beyond standard superradiance, or narrow Fano resonance-like peaks. We also show that the dipole-dipole interaction decays exponentially with distance as a result of retardation, with the range determined by the atomic linewidth. We discuss a proof-of-concept implementation of our results in a superconducting circuit platform.