Properties of upconverted entangled broadband light

We experimentally investigate the properties of light generated by the sequential processes of spontaneous parametric downconversion followed by upconversion. By interfering the upconverted photons with the original pump light, we show that the processes preserve the coherence of the light. Moreover, we observe interferences with doubled phase sensitivity when changing the phase of the downconverted entangled light, although its coherence length is several orders of magnitude shorter than the one of the pump light. Finally the statistics of the upconverted light is expected to be super-poissonian and we experimentally observe superbunching.