Spatiotemporal structure of biphoton entanglement in type-II parametric down-conversion

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

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Abstract

We investigate the spatiotemporal structure of the biphoton correlation in type-II parametric down-conversion (PDC). As in type-I PDC, we find that the correlation is nonfactorizable in space and time. Differently from type I, the type-II correlation in the spontaneous regime displays an asymmetric V-shaped structure in any cross section including time and one transverse dimension. This asymmetry along the temporal coordinate originates from the signal-idler group velocity mismatch and tends to disappear as the parametric gain is raised. We observe a progressive transition toward a symmetric X-shaped geometry similar to that found in type I when stimulated PDC becomes dominant. We also give quantitative evaluations of the localization in space and in time of the correlation, analyze its behavior for different crystal tuning angles, and underline qualitative differences with respect to type-I PDC.

Original languageEnglish
Article number013835
Number of pages14
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Volume82
Issue number1
DOIs
Publication statusPublished - 26 Jul 2010

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Keywords

  • parametric down-conversion
  • spatio-temporal structures
  • biphoton
  • parametric gain
  • quantitative evaluation

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