Noise Properties of a Josephson Parametric Oscillator

We perform noise spectroscopy of a Josephson parametric oscillator (JPO) by implementing a microwave homodyne interferometric measurement scheme. We observe the fluctuations in the selfoscillating output field of the JPO for a long 10-s time interval in a single-shot measurement and characterize the phase and amplitude noise. Furthermore, we investigate the effects of the pump strength on the output noise power spectra of the JPO. We find strong fluctuations in the phase with a 1/f (2) characteristic in the phase noise power spectrum, which are suppressed by increasing the pump strength.