Fig. 4
Fidelities of crossly established entanglement. The green bar represents entanglement established between S1 to R2, and the yellow bars represents S2 to R1. The pair-appeared bars represent the fidelities measured simultaneously. For each BSM, there are four possible outcomes, thus there are 16 situations. The red line represents the threshold of Fth = 0.9256. The fourfold coincidence is about three counts per second. We accumulate coincidences for 120 s, and total 720 counts for each two-state transition. The error bars are calculated assuming a Poisson statistics for the coincidence counts and Gaussian error propagation
