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.
Jain, N., Huisman, S. R., Bimbard, E., & Lvovsky, A. I. (2010). A bridge between the single-photon and squeezed-vacuum states. Optics express, 18(17), 18254-18259. https://doi.org/10.1364/OE.18.018254