Generation of multi-photon entanglement by propagation and detection

TL;DR

This paper explores how photon entanglement can be generated and manipulated through propagation and detection, revealing that unentangled photons can evolve into highly entangled states, including GHZ states, with specific symmetry properties.

Contribution

It demonstrates that propagation and post-selection can produce multi-photon entanglement from initially unentangled photons, including symmetric and GHZ states, expanding entanglement generation methods.

Findings

Post-selected entanglement varies with propagation distance.

Unentangled photons can evolve into maximally entangled states.

Generation of symmetric and GHZ states through propagation.

Abstract

We investigate the change of entanglement of photons due to propagation. We find that post-selected entanglement in general varies by propagation and, as a consequence, states with maximum bi- and tri-partite entanglement can be generated from propagation of unentangled photons. We generalize the results to n photons and show that entangled states with permutation symmetry can be generated from propagation of unentangled states. Generation of n-photon GHZ states is discussed as an example of a class of states with the desired symmetry.