Entanglement-based signature of nonlocal dispersion cancellation

TL;DR

This paper presents a quantum inequality that distinguishes entangled light from classical fields by demonstrating nonlocal dispersion cancellation, a phenomenon impossible to replicate classically.

Contribution

The authors derive a quantum inequality that can be violated by entangled photon pairs, providing a clear quantum signature of nonlocal dispersion cancellation.

Findings

Entangled photon pairs violate the derived inequality.

Classical fields cannot violate the inequality.

The result unambiguously demonstrates quantum nonlocality in dispersion cancellation.

Abstract

We derive an inequality bounding the strength of temporal correlations for a pair of light beams prepared in a separable state and propagating through dispersive media with opposite signs of group velocity dispersion. The presented inequality can be violated by entangled states of light, such as photon pairs produced in spontaneous parametric down-conversion. Because the class of separable states covers the entire category of classical fields as a particular case, this result provides an unambiguously quantum feature of nonlocal dispersion cancellation that cannot be reproduced within the classical theory of electromagnetic radiation.