Preparation of free-travelling three-mode W-type entangled squeezed vacuum states.

A scheme is proposed to prepare W -type entangled squeezed vacuum states (ESVSs) via free-travelling optical fields with simple linear optical devices, photo detectors and cross-Kerr medium. We investigate the influence of an inexact nonlinear phase factor between two modes on the fidelity of the prepared three-mode W -type ESVSs. By adjusting the appropriate reflectivity, the scheme can be extended to create 2 n + 1 -mode W -type ESVSs. [ABSTRACT FROM AUTHOR]