Fig. 3: Experimental data for discriminating quantum states using two-copy collective measurements.

In all three figures the shaded red region corresponds to the error probabilities accessible by local operations and classical communication (LOCC) measurements and the blue region corresponds to the error probabilities attainable by collective measurement. The blue markers correspond to the experimental data. Each data point corresponds to 200,000 shots. All data points include statistical error bars corresponding to one standard deviation obtained via bootstrapping, but in most cases the data points are larger than the error bars. The inset is included in the first figure to show the scale of the error bars. Each data point corresponds to a measurement optimised for that particular prior probability.