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Physical Review A

Four-photon W state using two-crystal geometry parametric down-conversion

Yongmin Li, Takayoshi Kobayashi

Published Jul 23, 2004• 31 citations
Publisher

Abstract

An experimental scheme for producing a four-photon entangled $W$ state directly from the parametric down-conversion of a two-crystal geometry is proposed. In our scheme, only linear optical elements and photon detectors are required. Sophisticated and fragile interferometric setups are unnecessary.

DOI
10.1103/physreva.70.014301

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An experimental scheme for producing a four-photon entangled WWW state directly from the parametric down-conversion of a two-crystal geometry is proposed. In our scheme, only linear optical elements and photon detectors are required. Sophisticated and fragile interferometric setups are unnecessary.
We propose two interesting methods of generating the four-photon W state. These methods use parametric down-conversion processes, linear optical elements, and commercial photon detectors, which are readily feasible under current technology. They can also be used to generate the three-photon W state, the three-photon Greenberger–Horne–Zeilinger state, and the three-photon maximally entangled photon-number state (a typical photon-number entanglement state) by simply changing some experimental components or their parameters. Moreover, assuming we have photon number-resolving detectors, these methods can develop into methods that generate a general n -photon W state. They are expected to become powerful tools for experimental investigations of multipartite entanglement and its applications to quantum information processing.
We propose two interesting methods of generating the four-photon WWW state. These methods use parametric down-conversion processes, linear optical elements, and commercial photon detectors, which are readily feasible under current technology. They can also be used to generate the three-photon WWW state, the three-photon Greenberger-Horne-Zeilinger state, and the three-photon maximally entangled photon-number state (a typical photon-number entanglement state) by simply changing some experimental components or their parameters. Moreover, assuming we have photon number-resolving detectors, these methods can develop into methods that generate a general nnn-photon WWW state. They are expected to become powerful tools for experimental investigations of multipartite entanglement and its applications to quantum information processing.