# Conventional and unconventional photon statistics

## TL;DR

This paper presents a unified framework to understand photon statistics in light-matter systems, distinguishing between conventional and unconventional mechanisms based on interference effects and resonance conditions.

## Contribution

It introduces a novel classification of photon correlations into conventional and unconventional types, providing a comprehensive theoretical framework for diverse light-matter systems.

## Key findings

- Unified description of photon bunching and antibunching
- Identification of resonance mechanisms for photon correlations
- Framework applicable to various light-matter systems

## Abstract

We show how the photon statistics emitted by a large variety of light-matter systems under weak coherent driving can be understood, to lowest order in the driving, in the framework of an admixture of (or interference between) a squeezed state and a coherent state, with the resulting state accounting for all bunching and antibunching features. One can further identify two mechanisms that produce resonances for the photon correlations: i) conventional statistics describes cases that involve a particular quantum level or set of levels in the excitation/emission processes with interferences occurring to all orders in the photon numbers, while unconventional statistics describes cases where the driving laser is far from resonance with any level and the interference occurs for a particular number of photons only, yielding stronger correlations but only for a definite number of photons. Such an understanding and classification allows for a comprehensive and transparent description of the photon statistics from a wide range of disparate systems, where optimum conditions for various types of photon correlations can be found and realized.