  The two modes of the Einstein-Podolsky-Rosen quadrature entangled state
generated by parametric down-conversion interfere on a beam splitter of
variable splitting ratio. Detection of a photon in one of the beam splitter
output channels heralds preparation of a signal state in the other, which is
characterized using homodyne tomography. By controlling the beam splitting
ratio, the signal state can be chosen anywhere between the single-photon and
squeezed state.
