Emitters of $N$-photon bundles

TL;DR

This paper introduces a cavity QED scheme for generating tunable, ultrabright sources of N-photon bundles with high purity, enabling new regimes like N-photon lasing and guns, surpassing traditional correlation measures.

Contribution

It proposes a novel method to produce and quantify N-photon bundles with high purity, extending the analysis to multi-photon regimes beyond standard correlation functions.

Findings

Achieves near 100% two-photon emission purity

Reaches 90% three-photon emission purity

Demonstrates regimes from N-photon lasing to N-photon guns

Abstract

We propose a scheme based on the coherent excitation of a two-level system in a cavity to generate an ultrabright CW and focused source of quantum light that comes in groups (bundles) of $N$ photons, for an integer $N$ tunable with the frequency of the exciting laser. We define a new quantity, the \emph{purity} of $N$-photon emission, to describe the percentage of photons emitted in bundles, thus bypassing the limitations of Glauber correlation functions. We focus on the case $1\le N\le3$ and show that close to 100% of two-photon emission and 90% of three-photon emission is within reach of state of the art cavity QED samples. The statistics of the bundles emission shows that various regimes---from $N$-photon lasing to $N$-photon guns---can be realized. This is evidenced through generalized correlation functions that extend the standard definitions to the multi-photon level.