Multiphoton Bell-type inequality: a tool to unearth nonlocality of continuous variable quantum optical systems

TL;DR

This paper introduces a multiphoton Bell-type inequality for continuous variable quantum systems, capable of detecting nonlocality in a broad range of states including noisy, Gaussian, and non-Gaussian states, advancing quantum nonlocality analysis.

Contribution

The paper develops a new Bell-type inequality applicable to four-mode continuous variable systems, extending nonlocality detection beyond two-photon states and including mixed and fluctuating photon number states.

Findings

Detects nonlocality in noisy Gaussian states

Applies to pure, mixed, Gaussian, and non-Gaussian states

Effective in identifying nonclassicality with beam splitter models

Abstract

We consider a multiphoton Bell-type inequality to study nonlocality in four-mode continuous variable systems, which goes beyond two-photon states and can be applied to mixed as well as states with fluctuating photon number. We apply the inequality to a wide variety of states such as pure and mixed Gaussian states (including squeezed thermal states) and non-Gaussian states. We consider beam splitters as a model for leakage and show that the inequality is able to detect nonclassicality of noisy Gaussian states as well. Finally, we investigate nonlocality in pair-coherent states and entangled coherent states, which are prominent examples of nonclassical, non-Gaussian states.