Superbunching and Nonclassicality as new Hallmarks of Superradiance

TL;DR

This paper explores superradiance in atomic ensembles, revealing new phenomena like superbunching and nonclassical light emission, and establishes conditions for these effects through photon-photon correlation analysis.

Contribution

It introduces the concepts of superbunching and nonclassicality as new hallmarks of superradiance, analyzing their occurrence in systems with doubly excited $W$ states.

Findings

Identification of conditions for nonclassical light emission.

Discovery of superbunching and superbunching phenomena.

Analysis of photon-photon cross correlations showing nonclassicality.

Abstract

Superradiance, i.e., spontaneous emission of coherent radiation by an ensemble of identical two-level atoms in collective states introduced by Dicke in 1954, is one of the enigmatic problems of quantum optics. The startling gist is that even though the atoms have no dipole moment they radiate with increased intensity in particular directions. Following the advances in our understanding of superradiant emission by atoms in entangled $W$ states we examine the quantum statistical properties of superradiance. Such investigations require the system to have at least two excitations as one needs to explore the photon-photon correlations of the radiation emitted by such states. We present specifically results for the spatially resolved photon-photon correlations of systems prepared in doubly excited $W$ states and give conditions when the atomic system emits nonclassial light. Equally, we derive the conditions for the occurrence of bunching and even of superbunching, a rare phenomenon otherwise known only from nonclassical states of light like the squeezed vacuum. We finally investigate the photon-photon cross correlations of the spontaneously scattered light and highlight the nonclassicalty of such correlations.