Two-mode Correlation of Microwave Quantum Noise Generated by Parametric Down-Conversion

In this letter, we report the observation of the correlation between two modes of microwave radiation resulting from the amplification of quantum noise by the Josephson Parametric Converter. This process, seen from the pump, can be viewed as parametric down-conversion. The correlation is measured by an interference experiment displaying a contrast better than 99% with a number of photons per mode greater than two hundred and fifty thousand. Dispersive measurements of mesoscopic systems and quantum encryption can benefit from this development.