X entanglement: the nonfactorable spatiotemporal structure of biphoton correlation

A. Gatti, E. Brambilla, L. Caspani, O. Jedrkiewicz, L. A. Lugiato

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)


We investigate the spatiotemporal structure of the biphoton entanglement in parametric down-conversion (PDC) and we demonstrate its nonfactorable X-shaped geometry. Such a structure gives access to the ultrabroad bandwidth of PDC, and can be exploited to achieve a biphoton 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 nonfactorability opens the possibility of tailoring the temporal entanglement by acting on the spatial degrees of freedom of twin photons.

Original languageEnglish
Article number223601
Number of pages4
JournalPhysical Review Letters
Issue number22
Publication statusPublished - 4 Jun 2009


  • femtosecond range
  • near fields
  • parametric down-conversion
  • spatial degrees
  • spatio-temporal structures
  • temporal localization
  • twin photons


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