A two-dimensional quarter bow-tie billiard (see inset) is used to test the CPA protocols. The red dot on the bow-tie represents the location of a point-like variable loss in the cavity. Through analysis of the S-matrix, two CPA states are found at the same system configuration. By injecting two different CPA waveforms, the measured ratios of output power Pout to input power Pin as a function of the microwave frequency are plotted together. The different incoming waveforms support two different CPA states with different CPA frequencies. The scale bar of the mean mode spacing Δ is shown in the plot as well.