Experimental Violation of Bell's Inequality in Spatial-Parity Space

TL;DR

This paper demonstrates the first experimental violation of Bell's inequality using spatial parity of entangled photons, confirming quantum nonlocality in the spatial domain with significant statistical confidence.

Contribution

It introduces a novel experimental approach to test Bell's inequality in spatial parity space using optical methods and entangled photon pairs.

Findings

Bell inequality violated with a value of 2.389 ± 0.016

Entanglement demonstrated in the spatial parity degree of freedom

Violation exceeds 24 standard deviations

Abstract

We report the first experimental violation of Bell's inequality in the spatial domain using the Einstein--Podolsky--Rosen state. Two-photon states generated via optical spontaneous parametric downconversion are shown to be entangled in the parity of their one-dimensional transverse spatial profile. Superpositions of Bell states are prepared by manipulation of the optical pump's transverse spatial parity--a classical parameter. The Bell-operator measurements are made possible by devising simple optical arrangements that perform rotations in the one-dimensional spatial-parity space of each photon of an entangled pair and projective measurements onto a basis of even--odd functions. A Bell-operator value of 2.389 +- 0.016 is recorded, a violation of the inequality by more than 24 standard deviations.