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Physical Review A

Four-photon entanglement from two-crystal geometry

Yongmin Li, Takayoshi Kobayashi

Published Feb 23, 2004• 7 citations
Publisher

Abstract

In this paper, a four-photon entangled state obtained directly from the down-conversion of a two-crystal geometry is analyzed. These two identically cut type-I crystals are oriented with their optic axes aligned in perpendicular planes. The applications of this kind of four-photon entangled state are also discussed.
DOI
10.1103/physreva.69.020302

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In this paper, we report a scheme for the generation of a pulsed polarization entangled-photon pair in a two-crystal geometry. These two crystals are oriented with their optical axes aligned in a perpendicular plane, stacked in the vertical direction. The stack direction and the pass direction of pump laser are orthogonal. This scheme has some advantages compared to other schemes: no time compensation or narrow-band filter is needed, it is insensitive to the thickness of the nonlinear crystal. As a demonstration of its workability, we get more than 86% high visibility of two-photon quantum interference experimentally for the polarization variable, without any time compensation and narrow-band filter. This scheme may be a useful technique for the generation of a pulsed entangled-photon pair.