# Hyperradiance from collective behavior of coherently driven atoms

## TL;DR

This paper introduces hyperradiance, a phenomenon where two coherently driven atoms in a cavity radiate more intensely than traditional superradiance, even under out-of-phase conditions, explained by photon cascades among Dicke states.

## Contribution

It reveals hyperradiance in a two-atom cavity system, exceeding superradiant effects, and provides a clear theoretical explanation involving Dicke state cascades.

## Key findings

- Hyperradiance surpasses superradiance in a two-atom cavity system.
- Strong quantum fluctuations accompany hyperradiance.
- The phenomenon occurs even with out-of-phase atomic radiation.

## Abstract

The collective behavior of ensembles of atoms has been studied in-depth since the seminal paper of Dicke [R. H. Dicke, Phys. Rev. 93, 99 (1954)], where he demonstrated that a group of emitters in collective states is able to radiate with increased intensity and modified decay rates in particular directions, a phenomenon which he called superradiance. Here, we show that the fundamental setup of two atoms coupled to a single-mode cavity can be distinctly exceeding the free-space superradiant behavior, a phenomenon which we call hyperradiance. The effect is accompanied by strong quantum fluctuations and surprisingly arises for atoms radiating out-of-phase, an alleged non-ideal condition, where one expects subradiance. We are able to explain the onset of hyperradiance in a transparent way by a photon cascade taking place among manifolds of Dicke states with different photon numbers under particular out-of-phase coupling conditions. The theoretical results can be realized with current technology and thus should stimulate future experiments.