30 Nov 2007
A team of researchers from Germany, Japan and Denmark have developed a system that can efficiently create highly entangled bipartite continuous variable polarization states.
The team produced polarization squeezed pulses by exploiting the Kerr non-linearity of a glass fiber. Polarization entanglement was then generated by interfering two independent polarization squeezed fields on a symmetric beam splitter (New J. Phys. 9 410)
To verify entanglement generation, the researchers characterized the quantum correlations of the system for two different sets of conjugate Stokes parameters, which showed that the degree of correlations depends critically on the beam-splitting ratio of the entangling beam splitter.
The set-up developed by the team has a number of advantages over previous fiber-based experiments. By employing the polarization rather than the quadrature variables, characterization of all relevant parameters is possible by simple direct detection. In addition, the single pass squeezing method avoids the intrinsic limitations of Sagnac loop squeezers, and noticeably improved squeezing can be generated, which in turn allows for improved entanglement generation.
The researchers say that their system is a suitable source of polarization entangled states for applications in quantum information and communication, particularly since detection is made easier by the fact that there is no need need for an external phase reference beam.