Boosting entanglement generation in down-conversion with incoherent illumination

TL;DR

This paper demonstrates that using partially coherent Gaussian pump beams in spontaneous parametric down-conversion can produce highly entangled photon states even with low coherence, challenging traditional assumptions.

Contribution

It introduces a novel class of partially coherent pump beams that increase entanglement inversely with coherence, enabling highly entangled states from incoherent light.

Findings

Entanglement increases as pump coherence decreases.

Incoherent pump beams can generate highly entangled multi-photon states.

This approach broadens the understanding of entanglement generation in quantum optics.

Abstract

Entangled photons produced by spontaneous parametric down-conversion have been of paramount importance for our current understanding of quantum mechanics and advances in quantum information. In this process, the quantum correlations of the down-converted photons are governed by the optical properties of the pump beam illuminating the non-linear crystal. Extensively, the pump beam has been modeled by either coherent beams or by the well-know Gaussian-Schell model, which leads to the natural conclusion that a high degree of optical coherence is required for the generation of highly entangled states. Here, we show that when a novel class of partially coherent Gaussian pump beams is considered, a distinct type of quantum state can be generated for which the amount of entanglement increases inversely with the degree of coherence of the pump beam. This leads to highly incoherent yet highly entangled multi-photon states, which should have interesting consequences for photonic quantum information science.