Improved entanglement indicators for optical fields and its application in the event-ready experiment for bright squeezed vacuum with induced non-gaussianity

TL;DR

This paper introduces improved variance-based entanglement criteria for four-mode optical fields, demonstrating their effectiveness on bright squeezed vacuum states with non-Gaussian features and proposing an experimental setup for event-ready tests.

Contribution

It presents more efficient entanglement conditions for four-mode optical fields using variances and proposes a practical scheme for generating relevant quantum states.

Findings

Enhanced entanglement detection for bright squeezed vacuum states.

Conditions outperform previous variance-based criteria.

Feasible experimental scheme for event-ready quantum state generation.

Abstract

Better versions of separability conditions for four mode optical fields, i.e. two beams with two modes of mutually orthogonal polarization are given. Our conditions involve variances. Their meaning is intuitive and their implementation is feasible. Namely, if for a given quantum state the spread of the data around its mean value is smaller than the minimal spread predicted for the set of separable states, then the given state is entangled. Our conditions are formulated for standard quantum Stokes observables and normalized Stokes observables and result to be more efficient that the previous conditions for four mode optical fields involving variances. We test our conditions for bright squeezed vacuum with (and without) induced non-gaussianity obtained by addition or subtraction of photons. Also we propose a practical experimental scheme of how to generate such states for an event-ready experiment.