Key points are not available for this paper at this time.
We present the results of an experimental effort to generate squeezed microwave radiation using the phase-sensitive gain of a Josephson parametric amplifier. To facilitate the interpretation of the experimental results, we first present a discussion of the theory of microwave squeezing via Josephson parametric amplifiers. This is followed by a detailed description of the device fabricated for our experiment. Experimental results are then presented for the device used in both the doubly degenerate or four-photon mode and for the degenerate or three-photon mode. We have observed parametric deamplification of signals by more than 8 dB. We have demonstrated squeezing of 4. 2-K thermal noise. When operated at 0. 1 K, the amplifier exhibits an excess noise of 0. 28 K when referred to the input. This is smaller than the vacuum fluctuation noise level /2k=0. 47 K. The amplifier is thus quieter than a linear phase-insensitive amplifier in principle can be.
Yurke et al. (Wed,) studied this question.