inequality is violated, i.e., jSj > 2, for all four Bell states produced with our
setup and (b) the violation occurs by up to 10 standard deviations ()of
measurement uncertainty.
To ascertain the degree of entanglement produced by the true FPS events in our
setup, the accidental coincidences resulting from the uncorrelated background
photons and the dark counts in the detectors were measured for each set of data
acquired in the three polarization-entanglement experiments described above. The
rate of accidental coincidences was as large as the rate of “true” coincidences,
plotted in Figure 21.8 by subtracting the accidental coincidences, and the raw
visibility of TPI was only ’30%. We believe, the majority of background photo ns
in our setup arise