  The interferometers of Hanbury Brown and collaborators in the 1950s and 60s,
and their modern descendants now being developed (intensity interferometers)
measure the spatial power spectrum of the source from intensity correlations at
two points. The quantum optical theory of the Hanbury Brown and Twiss (HBT)
effect shows that more is possible, in particular the phase information can be
recovered by correlating intensities at three points (bispectrum). In this
paper we argue that such 3 point measurements are possible for bright stars
such as Sirius and Betelgeuse using off the shelf single photon counters with
collecting areas of the order of 100m2. It seems possible to map individual
features on the stellar surface. Simple diameter measurements would be possible
with amateur class telescopes.
