Three Photon Entanglement from Ortho-Positronium Revisited

TL;DR

This paper re-analyzes three-photon entanglement from ortho-positronium decay, revealing previously unnoticed phases and emphasizing the importance of a fixed spin quantization axis for understanding photon correlations.

Contribution

It introduces a comprehensive three-dimensional formalism for analyzing photon entanglement from ortho-positronium decay, highlighting new phase effects related to spin orientation.

Findings

Non-negligible phases in entangled states even when spin is perpendicular to decay plane

Advocates for a fixed spin quantization axis for generality

Discusses differences between 3D and 2D photon correlation formalisms

Abstract

Entanglement of three photons from the decay of ortho-positronium is re-analyzed. We use the full three body phase space to write down the entangled states classified according to the spin directions of the ortho-positronium. Even in the case when the spin is perpendicular to the decay plane, we find non-negligible phases entering the entangled state. This has not been noticed before. We advocate a fixed quantization axis of the spin for the sake of generality. A brief discussion of a three dimensional formalism for photons, including correlations, versus a two dimensional one is given.