  We report experimental evidence that the microwave electromagnetic field
generated by a normal conductor, here a tunnel junction placed at ultra-low
temperature, can be non-classical. By measuring the quadratures of the
electromagnetic field at one or two frequencies in the GHz range, we
demonstrate the existence of squeezing as well as entanglement in such
radiation. In one experiment, we observe that the variance of one quadrature of
the photo-assisted noise generated by the junction goes below its vacuum level.
In the second experiment, we demonstrate the existence of correlations between
the quadratures taken at two frequencies, which can be stronger than allowed by
classical mechanics, proving that the radiation at those two frequencies are
entangled.
