  Three-dimensional imaging is one of the crucial tools of modern sciences,
that allows non-invasive inspection of physical objects. We propose and
demonstrate a method to reconstruct a three-dimensional structure of coherence
stored in an atomic ensemble. Our method relies on time-and-space resolved
heterodyne measurement that allows the reconstruction of a complex
three-dimensional profile of the coherence with a single measurement of the
light emitted from the ensemble. Our tomographic technique provides a robust
diagnostic tool for various atom-based quantum information protocols and could
be applied to three-dimensional magnetometry, electrometry and imaging of
electromagnetic fields.

Quantum Physics;Atomic Physics;Optics