X-entanglement of PDC photon pairs

TL;DR

This paper explores the complex X-shaped spatio-temporal entanglement structure of photon pairs generated by parametric down-conversion, revealing its potential for ultra-fast temporal localization and entanglement tailoring.

Contribution

It demonstrates the non-factorable X-shaped geometry of bi-photon entanglement in PDC and discusses its implications for ultrafast quantum applications.

Findings

Revealed the X-shaped non-factorable entanglement structure.

Achieved femtosecond-scale temporal localization of photon pairs.

Showed the possibility to tailor temporal entanglement via spatial degrees of freedom.

Abstract

We investigate the spatio-temporal structure of the bi-photon entanglement in parametric down-conversion (PDC) and we demonstrate its non-factorable X-shaped geometry. Such a structure gives access to the ultra-broad bandwidth of PDC, and can be exploited to achieve a bi-photon temporal localization in the femtosecond range. This extreme localization is connected to our ability to resolve the photon positions in the source near-field. The non factorability opens the possibility of tailoring the temporal entanglement by acting on the spatial degrees of freedom of twin photons.