Interferometric measurement of the biphoton wave function
  Interference between an unknown two-photon state (a "biphoton") and the two-photon component of a reference state gives a phase-sensitive arrival-time distribution containing full information about the biphoton temporal wave function. Using a coherent state as a reference, we observe this interference and reconstruct the wave function of single-mode biphotons from a low-intensity narrowband squeezed vacuum state. 
Federica A. Beduini, Joanna A. Zieli\'nska, Vito G. Lucivero, Yannick   A. de Icaza Astiz and Morgan W. Mitchell
quant-ph