Extended Data Fig. 2: Quadrature measurements.
From: Stationary entangled radiation from micromechanical motion
a, System calibration of output channel 1 (top) and 2 (bottom). The measured noise density in units of quanta, Si = (Ni/ζi) − nadd,i, is shown as a function of the temperature T of the 50-Ω load. The error bars indicate the standard deviation obtained from three measurements with 28,800 quadrature pairs each. The solid lines are fits to equation (5) in units of quanta, which yields the system gain and noise with the standard errors (95% confidence interval) stated in the main text. The insets show the phase space distribution with the pump tones turned off. These two-variable quadrature histograms are based on 604,800 measured quadrature pairs for each channel. b, Difference of the two-variable quadrature histograms with the pumps turned on and off for all quadrature-pair combinations in units of quanta (as calibrated in a), obtained using 216,000 pairs from both channels.
