Extended Data Fig. 7: Two-photon quantum interference.

a, Histogram for coincident events measured by two single-photon detectors in a two-photon quantum interference experiment, measured by cross-referencing photon detection events from a pulse train of 10 optical π pulses that excite both emitters. Hong–Ou–Mandel interference of simultaneously coinciding photons ideally results in vanishing coincidence events within a single excitation round. The time difference between individual excitation rounds is 1 μs. Histograms of coincidence counts are shown with a bin-size of 5 ns. b, Total number of coincidences as a function of the number of pulses separating the two detection events. We extrapolate the measured coincidences to infer the expected coincidences for distinguishable photons at zero pulse difference by fitting a linear regression (orange). Using this to normalize the 22 observed coincidences for zero pulse difference allows us to estimate the two-photon quantum interference visibility V = 0.90(2). Error bars are 1 s.d.