Azimuthal angular entanglement between decaying particles in ultra-peripheral ion collisions

TL;DR

This paper explores quantum entanglement in azimuthal angles of particles produced in ultra-peripheral ion collisions, comparing classical and quantum predictions and highlighting potential for multi-particle entanglement tests.

Contribution

It introduces a comparison between classical and quantum models of azimuthal correlations in UPCs, emphasizing the potential for observing multi-particle entanglement.

Findings

Quantum and classical predictions of azimuthal correlations differ significantly.

UPC processes can produce multi-particle entangled states with shared polarization.

Potential for new tests of multi-particle quantum entanglement.

Abstract

Ultra-peripheral collisions (UPCs) involving relativistic heavy ions are a unique laboratory to study quantum correlations. The intense electromagnetic fields generate high rates of photonuclear interactions, including events involving multiple photon exchange. Multiple photon exchange can result in the production of multiple vector mesons and/or nuclear excitations. These interactions share a common impact parameter, so the photons have the same linear polarization. The shared polarization entangles the particles, leading to unique quantum correlations. The decays of these vector excitations are sensitive to this polarization, allowing for the study of these correlations. This letter will compare classical and quantum calculations of the correlations between these azimuthal directions. The two approaches predict vert different angular correlations. The differences are akin to those seen with polarized photons in tests of Bells inequality. Uniquely, UPC photoproduction can produce final states containing three or more particles, all entangled with the same polarization. These more complex states exhibit additional unique phenomenology, allowing new tests of multi-particle entanglement.