  The quantum statistical interference between identical particles emitted from
a completely chaotic source is expected to provide valuable input for the space
time description of the system. Intensity interferometry of thermal photons
produced in heavy ion collisions is a very promising tool to explore the
structure and dynamics of the collision fireball. Thermal photons having $K_T
\, \le \, 2$ GeV/$c$ get competing contribution from both hadronic and quark
matter phases and this competition gives rise to a rich structure in the
outward correlation function, owing to the interference between the photons
from the two sources. The temporal separation between the two sources provides
the lifetime of the system and the correlation results are found to be
sensitive to quark hadron phase transition temperature and the formation time
of the plasma. The outward correlation function strongly depends on the
equation of state of the strongly interacting matter and is seen to clearly
distinguish between the lattice based and bag model equations of state.
