Photonic Entanglement and Polarization Nonclassicality: Two Manifestations, One Nature

TL;DR

This paper establishes a theoretical and experimental equivalence between nonclassical polarization and photon entanglement, unifying two quantum phenomena and highlighting nonclassical polarization as a valuable resource for quantum technologies.

Contribution

It demonstrates the strict equivalence between nonclassical polarization and photon entanglement, providing a unified framework and experimental verification of their relationship.

Findings

Nonclassical polarization is equivalent to photon entanglement.

The equivalence is basis-independent and experimentally verified.

Nonclassical polarization is a practical resource for quantum protocols.

Abstract

We demonstrate in theory and experiment the strict equivalence between nonclassical polarization and the entanglement of indistinguishable photons, thereby unifying these two phenomena that appear dissimilar at first sight. This allows us to analyze nonclassicality and multi-photon entanglement within the same framework. We experimentally verify this double-sided form of quantumness and its independence from the polarization basis, contrasting other notions of coherence that are highly basis-dependent. Our findings show how nonclassical polarization turns out to be equally resourceful for quantum protocols as entanglement, emphasizing its importance in practical applications.