Parametric amplifier gain. (a) vs. pump tone detuning δ and drive strength ξ at zero signal detuning Δ and for . For increasing drive strength ξ the detuning for maximum gain is indicated by the dashed white line. A cut through the data for the highest value is shown as the solid white line in the bottom part. (b) Gain as a function of signal detuning Δ for the indicated drives strengths and optimal pump detuning. The exact gain curves (solid lines) are well approximated by Lorentzian lines (black dashed lines).