Subradiance generation in a chain of two-level atoms with a single excitation

TL;DR

This paper investigates how subradiance emerges dynamically in a chain of two-level atoms with a single excitation, analyzing different initial conditions and laser excitation to inform future experimental detection.

Contribution

It introduces a dynamic approach to study subradiance in atomic chains, focusing on the evolution from initial excitation states rather than just spectral properties.

Findings

Subradiance can be generated under various initial excitation conditions.

Switching a weak laser on and off can induce subradiance.

The study provides insights for experimental detection of subradiance.

Abstract

Studies of subradiance in a chain N two-level atoms in the single excitation regime focused mainly on the complex spectrum of the effective Hamiltonian, identifying subradiant eigenvalues. This can be achieved by finding the eigenvalues $N$ of the Hamiltonian or by evaluating the expectation value of the Hamiltonian on a generalized Dicke state, depending on a continuous variable k. This has the advantage that the sum above N can be calculated exactly, such that N becomes a simple parameter of the system and no more the size of the Hilbert space. However, the question remains how subradiance emerges from atoms initially excited or driven by a laser. Here we study the dynamics of the system, solving the coupled-dipole equations for N atoms and evaluating the probability to be in a generalized Dicke state at a given time. Once the subradiant regions has been identified, it is simple to see if subradiance is being generated. We discuss different initial excitation conditions that lead to subradiance and the case of atoms excited by switching on and off a weak laser. This may be relevant for future experiments aimed at detecting subradiance in ordered systems.