What particles that never met "know" of one another?

TL;DR

This paper analyzes an experiment where identical particles from different sources exhibit quantum correlations without ever having interacted, highlighting nonlocal effects in quantum mechanics.

Contribution

It demonstrates how non-factorizable wave functions and symmetry properties can emerge at a distance without particle interaction, extending previous experimental setups.

Findings

Particles can exhibit symmetry or antisymmetry without meeting.

Wave function becomes non-factorizable when source information is indistinguishable.

Quantum correlations can be established at a distance without direct interaction.

Abstract

An experiment proposed by Yurke and Stoler, and similar to that realized experimentally by Sciarrino et al., is analyzed. In Sciarrino's realization, identical photons from a degenerated down-conversion pair are used, i.e. the photons met in the past. In the experiment analyzed here the particles are also identical, but from different sources. As long as one can tell from which source came each particle, the joint wave function remains factorizable. However, a configuration is created in which one cannot tell anymore which particle came from which source. As a result, the wave function becomes non-factorizable, symmetrical (for bosons) or antisymmetrical (for fermions). In part of the cases the situation is even more surprising: the particles never meet, s.t. the symmetry (antisymmetry) is produced at-a-distance without the particles having had the possibility to interact in any way.