(a) The experimentally measured values of the intrinsic error probability P* (solid circles) and the theoretically calculated values, using the estimated experimental parameters (shaded area, delimited by solid lines) as a function of the total loss of Bob's photon. The parameters are the mean number of photon pairs generated μ, the transmission of Alice's channel ηA, the probability of a dark count per 400-ps detection window for Alice's (Bob's) detectors dA (dB), and the fidelity F of the generated entangled state with respect to state |Φ+>. We used μ=0.032±0.004, ηA=7.56±2.23%, dA=4×10−8, dB=2.5×10−5, F=97.8±0.3% (Supplementary Table S1). Also shown are the values of PC* (hollow circles) corresponding to our measured values of PA and PB, as well as the theoretically calculated values (shaded area delimited by dashed lines). (b) Theoretically calculated values of P* (solid line) and PC* (dashed line) as a function of the total loss of Bob's photon assuming ultra-low-noise detectors for Bob, that is, dB=10 Hz×400 ps=4×10−9, and slightly improved experimental conditions, that is, μ=0.005, ηA=9.8%, dA=4×10−8, F=99.25%.