# Nonclassicality and entanglement for wavepackets

## TL;DR

This paper develops new criteria and measures for assessing total entanglement and nonclassicality in broadband wavepackets, addressing limitations of mode-entanglement measures for complex quantum emissions.

## Contribution

It introduces novel criteria for total entanglement and nonclassicality of wavepackets, applicable to broadband emissions and compatible with near-field detection.

## Key findings

- Criteria for total entanglement of wavepackets introduced
- Entanglement of wavepackets with ensembles analyzed
- Nonclassicality linked to mode entanglement and noise reduction

## Abstract

Mode-entanglement based criteria and measures become insufficient for broadband emission, e.g. from spasers (plasmonic nano-lasers). We introduce criteria and measures for the (i) total entanglement of two wavepackets, (ii) entanglement of a wavepacket with an ensemble and (iii) total nonclassicality of a wavepacket~(WP). We discuss these criteria in the context of (i) entanglement of two WPs emitted from two initially entangled cavities (or two initially entangled atoms) and (ii) entanglement of an emitted WP with the ensemble/atom for the spontaneous emission and the single-photon superradiance. We also show that, (iii) when the two constituent modes of a WP are entangled, this creates nonclassicality in the WP as a noise reduction below the standard quantum limit. The criteria we introduce are, all, compatible with near-field detectors.