Temporal coherence and correlation of counterpropagating twin photons

TL;DR

This paper investigates the temporal coherence and correlation properties of counterpropagating twin photons generated via spontaneous parametric-down conversion, revealing how pump pulse duration influences entanglement and spectral asymmetry.

Contribution

It provides a detailed analysis of how pump pulse duration affects the entanglement and spectral characteristics of counterpropagating twin photons in nonlinear crystals.

Findings

Different coherence regimes depending on pump pulse duration.

Transition from highly entangled to nearly separable states.

Asymmetric spectral properties of the photons.

Abstract

This work analyses the temporal coherence and correlation of counterpropagating twin photons generated in a quasi-phase matched nonlinear cristal by spontaneous parametric-down conversion. We find out different pictures depending on the pump pulse duration relative to two characteristic temporal scales, determined respectively by the temporal separation between the counter-propagating and the co-propagating wavepackets. When the pump duration is intermediate between the two scales, we show a transition from a highly entangled state to an almost separable state, with strongly asymmetric spectral properties of the photons.