Predicting correlations in superradiant emission from a cascaded quantum system

TL;DR

This paper introduces a scalable simulation method based on the truncated Wigner approximation for spins, enabling prediction of higher-order correlations in superradiant emission from large cascaded quantum systems, which was previously challenging.

Contribution

We developed a new stochastic simulation technique using the truncated Wigner approximation for spins to predict correlations in large cascaded quantum systems.

Findings

Successfully predicted second-order coherence function $g^{(2)}$ for superradiant emission.

Provided a scalable method for analyzing large cascaded quantum systems.

Demonstrated effectiveness in systems with up to a thousand atoms.

Abstract

In recent experiments, a novel type of cascaded quantum system has been realized using nanofiber-coupled cold atomic ensembles. This setup has enabled the study of superradiant decay of highly excited collective spin states of up to a thousand atoms, featuring unidirectional coupling mediated by the waveguide mode. The complexity arising from the large, multi-excited ensemble and the cascaded interactions between atoms makes conventional simulation methods unsuitable for predicting the correlations of superradiant emission beyond the first order. To address this challenge, we developed a new simulation technique based on the truncated Wigner approximation for spins. Our stochastic simulation tool can predict the second-order quantum coherence function, $g^{(2)}$, along with other correlators of the light field emitted by a strongly excited cascaded system of two-level emitters. This approach thus provides an effective and scalable method for analyzing cascaded quantum systems with large numbers of particles.