  Since its discovery, the "ghost" diffraction phenomenon has emerged as a
non-conventional technique for optical imaging with very promising advantages.
However, extracting intensity and phase information of a structured and
realistic object remains a challenge. Here, we show that a "ghost" hologram can
be recorded with a single-pixel configuration by adapting concepts from
standard digital holography. The presented homodyne scheme enables phase
imaging with nanometric depth resolution, three-dimensional focusing ability,
and shows high signal-to-noise ratio.
